welcome to "the whole story." i'm anderson cooper in tel aviv. the october 7th attack by hamas, left at least 1,400 people dead, 200 people held hostage according to israeli officials and many more people are still unaccounted for. in response, israel began a bombing campaign in gaza. according to the hamas health ministry, 4,000 have died so far. the story of hamas is complex. its roots date back to thehe formatioion of israel in 1948. it has many factions, including the so-called military wing that perpetrated the terror attack. sara sidner brings us the whole story on hamas, how they were warmed, what the ideology is and how they evolved over the decades. some of the images you see in this hour may be disturbing. >> pure, unadulterated evil. >> i can't even try to comprehend these monsters. >> terrorists. >> this is not islam. >> they should be spit out. >> we cannot expect that israel will continue to blockade gaza. >> deprive them of their freedom and assume they will not resist. at some point, it will boil over. >> october 7th was different. october 7th change everything. >> what happened on october 7th was absolutely unprecedented. hamas has targeted israeli civilians before. that's not new. what is new is simply the scale and the ruthlessness. >> how do you define hamas? who and what is hamas? >> hamas primarily is a social religious, political movement. >> hamas is seen by most palestinians as prt of the social fabric. there's plenty that cannot stand hamas. but some of their neighbors and family members are hamas supporters. hamas has several different aspects to it. it is certainly does have a military wing. it also has a political swing. it has social services. it sees itself as a movement. it's the movement and the movement is a comprehensive one. >> hamas is a nationalist movement that's committed to the notion of armed struggle. for the liberation of palestine. out of all of the palestine factions that exist, hamas is the only party that has an organized military. and a very well-resourced military farce. what that means is for many palestinians, hamas is the only party that can defend palestinian civilians against israeli aggression. >> that's the reality. that's how many palestinians view and consider them. a line of defense. >> since 2007, hamas has governed the gaza strip, a 25-mile-long, 7-mile-wide stretch of land, with 2 million people cut off from the world by an israeli blockade. an area humanitarian rights group have called an open-air prison. but the rise of hamas and what led up to its massacre of more than 1,000 men, women and children in israel is a story that begins long before hamas ever existed. >> this did not start on october 7th. ♪ >> troop reinforcements disembark to protect the holy land from disorder. >> the british had a mandate to govern palestine after world war i. and it said, you should prepare this territory for independence and facilitate a jewish national home. >> the british try mechanisms to make them agree on some kind of settlement. >> the british found they couldn't do both. they gave up. they left after world war ii. and they handed the problem over to the u.n. and said, we can't deal with it. >> the palestine problem moves to another stage of discussion. >> the u.n. sets up a commission that comes to a conclusion that the best solution is to take this land and to divide it, roughly speaking, half to the palestinians, half to the israelis. the jews accept that deal. the arabs do not. >> and so, war broke out. >> arabs and jewish nationals fought each other bitterly and re relentlessly. >> the state of israel declared itself and took control, not simply of the territory that the u.n. allotted to it, but other territory, as well, a lot of it has significant palestinian population. >> the new jewish state, israel, was born in a bath of blood. >> the birth of the state of israel for the palestinians is the catastrophe. in order to pave the way to accomplish israel as a jewish state, there needed to be an ethnic cleansing of palestinians. more than 700,000 palestinians fled outside of palestine. and palestine was decimated. >> women flee with what belongings they can carry. >> and israel said we're not allowing them to return. you may have thought you were leaving for a week. but you're never coming back. >> by the end of 1948, a newly formed israel had claimed 78% of the land of palestine. the palestinians that hadn't fled, settled in the 22% of land that israel had yet to conquer. >> what is left is the west bank in gaza. egyptians control gaza. the jordanians control the west bank. and that's how it was until the 1967 war. when arab armies amassed on israel's border. >> on the frontier of the gaza strip, a mere kilometer away. >> 1967 is one of the biggest historic moments in the middle east. israel launches a surprise attack against iz egypt. >> the israelis conquer the west bank and gaza. this is a moment of great exhilaration in israel because they feel they have defeated the arab armies in extraordinary military success. they have not figured out what they are going to do with the millions of palestinians on that land. >> the millions that fled to gaza, are under israeli occupation. >> that left all of the people citizens of nowhere. they weren't citizens of the israeli state. they were just stuck. >> mrpalestinians say, we need liberate ourselves. >> throughout the '70s and '80s, bursts of violence between palestinians and israelis were common place. the palestinian liberation organization, which was formerly led by the world, was led by yasser arafat, who led in exile outside of the palestinian territories. but inside israeli occupied gaza, a new resistance movement was under way. >> the first intifadah was one of the biggest mobilization of palestinian civil society and actors against the military occupation. and the itdea was they would disrupt the occupation operators. they refused to open shops. they blocked highways. it was a period of significance agitation. >> around the same time, islamists were shifting aproesh, to a more aggressive approach. and a new armed resistance group would emerge, officially known as hamas. >> he was a spiritual leader. in the gaza strip. one of the earliest founders and leaders of the muslim brotherhood chapters. when hamas emerged, he was the leader of the movement and the spiritual guide of the movement. >> hamas was not interested in liberating gaza and the west bank alone. instead, it set out to liberate israel altogether, as outlined in the 1988 charter, a goal that made hamas an outsider to peace negotiations, including the oslo accords. >> the oslo accords set off earthquakes. >> as our walls have been long, so much our hilling with swift. >> the oslo accords ultimately resulted in, the plo recognized the state of israel. and so, conceded 78% land of hysteric palestine. and israeli government recognized the plo as the sole, legitimate representative of the palestinian people. there was jubilation globally. and many palestinians, believe this might pave the way to the establishment of a state on 22% of their land. but this was, by no means, noncontroversial or unchallenged. and for hamas, this is something they were fundamentally opposed to. >> those negotiations never got off the ground. and one of the reasons was this upsurge of violence. >> one of the deadliest attacks to derail peace came in february of 1994. just months after the signing and historic white house photo op. >> a jewish center entered the mosque when people were worshiping there. >> that was a turning point because hamas then decided to begin employing suicide bombings as a form of resistance. >> 41 days after the mosque attack, hamas responded, detonating its first lethal suicide attack, killing seven israelis at a bus stop. >> the big reason oslo failed was violence. the adversary is not serious. israeli saying arafat is not stopping terrorism, palestinians say, the israelis are dragging their feet. they are increasing settlement building, even as they make promises they are going to leave. >> the fundamental reason that hamas has gained strength is that the palestinian authority, which is their competition, has been seen as feckless, corrupt, and unable to deliver on its core promise, which was a palestinian state. >> but to the west, hamas was not a negotiating partner. instead, it became a threat. in 1997, the u.s. designated h hamas a foreign terrorist organization. >> if you protest nonviolently, you are shot at. thigh left one avenue, which is armed resistance. >> hamas has decided it is going to use violence. and use violence against civilians. >> over the next decade, hamas continued its violence. and would meet more violence in return. will they go home with a deal? the latest from camp david. >> the wooded maryland retreat of u.s. presidents, camp david, was the site of a potentially historic summit in the summer of 2000. >> you had yasser arafat, the legendary leader of the palestinian liberation organization, who had a lot of credibibility withth palestinin. you had ehud barak, distinguished israeli figure, now prime minister. and you had bill clinton. >> their goal, end decades of hostilities, forge a palestiniaian/israeli i peace accordrd. >> i if they cannot makeke prog now, thehere will be more hostility and more bitterness. >> it seemed as though they had kind of come to an agreement. and arafat pulls out at the best minute, best he could well, because he believed if he did this, hamas would gain power. >> the israeli story on camp david is that advertise really prime minister offered significant concessions and the palestinians said no. the palestinian view was that the israelis and united states were going to give them offers they could not accept, and they were made to look bad. >> a former israeli defense minister, who many call the butcher of beirut, for the invasion of lebanon, made a provocative visit to the temple mount. a holy site in christianity, judaism and islam. it's a flash point of contention who should control it, israelis or arabs. >> the violence erupted. >> just the first sparks of what became the second inlt intifada. a violent clash over the west bank and gaza. the sect intifadah would last nearly five years. a half-decade fight that hamas became known for the routine use of terror and destruction. >> overtrtime, morore and d mor israel came to range as hamas' weapons got better and better. and the number of rockets increased. >> israeli forces demolished 4,000 palestinian homes and arrested thousands. israel shut down and bombed ministries and infrastructure, trying to coerce palestinian leaders to end the violence. between 2000, and 2005, there were over 3,300 registered fatalities. of palestinian to israeli ratio of 3/1. finally, in february 2005, came this announcement from the palestinian authority and israel. >> we have agreed with the prime minister ariel sharon, to seize all acts of violence. >> later that year, israel began to implement its disengagement plan, to evacuate israel se sett settlements. and military posts from gaza and a section of the west bank. thouousands of s settlement t resisidents lostst their homes. >> i it was a physysical a and pspsychologicacal disengagememe behalf of the israelis from gaza. it was no longer their problem. >> that was a difficult, painful step for israel to take, to pull settlers out. and how did palestinians respond? by shootining rockets.s. and therere is some e truth to . it's's also trueue, when i isra pulllled out of gaza, it contind to envelop it in a black cade. >> a blockade to isolate hamas and attempt to prevent smuggling of weapons. but it limited the transpoport necessitities for papalestinian citizensns in gagaza.. >> t there was an immedidiate cocollapse to o the qualitity o in gaza. medicines,s, food itemems. water.r. all of the items of a normal life were immediately suspended. the e immediate e impapact w wa sisignificant increase of popov. >> t the yoooors of the e israe disengagagement of g gaza in 20 leading up to elections in 2006, saw unprecedented wave of violence. i remember being in the city and feeling unsafe to simply go out about my wife in the s streets. >> andnd from gaza, hamas continued d to terrorizeze isra. >> israel isis d despite palestiniaians being impmprison it couldld expect cacalm. what h hamas was doioing, was shattering that resolution. every few months it would fire rockets to force israel to reconsider. >> in 2006, a year after announcement of the cease-fire, elections for the palestinian legislative council were held in gaza. cnn chief correspondent christiane amanpour covered the electition and its aftermath. >> it was clear that election was insisted on by the adadministratition of gegeorge h and cocondoleezza a rice and th group p of americansns who beli the iriraq w war o of 202003 w g democracacy to the w wider midd east. this was a very flawed assumption. the americans insisted on this election. even t though the e israelis a e palestininian authorority warnre united s states not to let t th elecection go ahead because the feared hamas would prevail. that's exactly what happened. >> the hamas victory was resounding, winning 76 of 132 seats of legislature. shocking results for the u.s. and israeli officials, bringing to power, a group the united states had designated as a terrorist organization. but a group that was making the difference in the lives of everyday palestinians. >> for many palestinians, hamas is a lifeline. for two decades, they built a grassroots network of affordable social services, like this medical clinic, that charges $2 a vivisit. >> t they providided educatitio. > they were well-entrenched with the citizens and civilians. that's one of the reasons why hahamas won inin gaza. in 2006. >> so, after t the 2006 victory is it under hamas? and who runs parts of gaza? hamas is worried there's a coup. and there is a coup. >> the coup in 2007, known as the battle of gaza, was relatively brief. and left no doubt that hamas was not part of the palestinian authority that governed the west bank. hamas was a more extreme a and violent group, now solely in charge of gaza. >> it seizes power and goes after the individuals associated with the palestinian authorities. some are thrown from windows. many are arrested and tortured. >> one thing is clear. hamas managed to do what fatah was unable to do prior to o 200 which h was to sececure ththe s in gaza. to put an end to the rampant lawlessness we were seeing. >> having hamas in charge of gaza meant the blockade woululd continueue. >> so, the cutoff of goods going in and out of gaza, have a big impact on hamas. they make it hard to provide prosperity to gazgagagazans.. >> hamamas was n not a populula movevement. ththere's no e elections.. there's s no way to o get rid o them or anything like that. people in the gaza strip just lived with them. >> and the conflict wbetween israel and hamas would not abate. hamas attacking israel. >> we just heard one explosion going off. it came from that jdirection ovr there. >> israel firing on gaza. i reported from gaza and israel, telling stories of destruction and dismay. >> around 3:30, a massive explosion. we know there's been four bomb boardments. >> it would escalate in 2014, after the israel security agency, identified hamas members as responsible of kidnapping and killing of three israeli teenagers from a jewish settlement in the west bank. weeks later, the abduction and murder of a palestinian teen, whose body was found in jerusalem. outrage and anger on both sides erupted in the 2014 gaza war. > israeael l put totogether operation, that consisted about 50 days, with 70,000 israeli call-ups. they went t into g gaza. threree differenent axis. that resulted in 66 israeli deaths and 6 israeli citizens. u.n. estimates 2,100 palestinian and hamas deaths during g that same operation. after that, the israeli government started taking a different look at ra mass and what they were doing in the gaza strip. more than 2,100 palestinians were killed. 60 israeli soldiers were killed. >> going in, in 2014, into gaza, after that sustained bombing, you had this huge sense of, the utter scale of the destruction. it was really hard. near impossible to find anyone who genuinely supported what hamas had done. >> i hope god won't let anyone taste our suffering, this woman in gaza said. >> the west bank, the year 2021, was a bloody year. >> a flash point, of eviction of palestinian families, some have been living there for generations. >> since prime minister benjamin netanyahu's re-election in 2009, there were 14,000 instances were palestinians were removed from their land by israeli settlers. this includes east jerusalem. >> sirens going off around jerusalem. this usually means there is a potential of rockets coming in. > 202021 wawas the firsrst t the e palestiniaians mobilizize single peoeople. demanding a single thing, to dismantle the regime of apartheid. for hamas, it's the protecting the mobilization of palestinians. >> israel, once again, fires back. >> 11 days of bloodshed. 11 days that killed almost 250 palestinians in gaza, according to the palestinian health ministry and 12 israelis. >> conditions in gaza since 2021 in particular, have been hellish. >> if there's a hell on earth, it's the lives of children in gaza. >> children make up nearly half of gaza's population. in part, because palestinians there simply don't get a chance to grow old. the unemployment rate for adults there is 40%. >> the israeli blockade e is ve tight. it makes it hardrd for people i gaza to have normal lives of any kind. and it is also true, when israelis have allowed things in, those materials are often used by hamas to turn into weapons. >> july 19th, 2023, less than three months before hamas' attack on israel. gaza is stronger, its army is mightier and its weapons are more advance. there's a lot of evidence that shows they are going into educational institutions to look for people who would be willing to die for the cause. there's also evidence they look for people with engineering aptitude and ability to design different explosive devices. >> hamas has had no shortage of military recruits. in 2023, i visited a military training class at a gaza high school. a visit facilitated by education ministry. one of the things high school students don't need to be taught is what it feels like to be in war. they have experienced it. they believe the fight between gaza and israel will never end. i've lost three people dear to me in the war. what has grown is the labyrinth of tunnenels under gaza. >> o over the lalast ten yeaear hamas has extpanded the tunnels. it was 100 miles or so. now, it's greater. >> we work around the clock in the tunnels. >> the tunnels are vital, they allow them to get to the firing posisitions for the rockets.s. allolow them to o move ammununi. >> i it's half t the size of th new york subway system. like they have built an underground city. >> the military leader, commander of hamas, he's been out of sight. as far as anybody knows, he's been living in tunnels for the last ten years. > the guest. >> he is k known as the guest t becacause for many, , many year now, he's reputed never to have spent night in the same place twice. this is his boss, the leader of all of hamas in gaza. >> there's an argument that hamas' line has hardened since 2017. he spent 20-plus years as a prisoner of the israelis. he speaks hebrew. >> hamas' hardened leadership, combined with renewed foreign support. >> there were meetings between the head of egyptian intelligigence in gagaza i itse. built up the suppoport f from i. >> i iran has prprovided m mill tens o of mimillions or more t hamas. > iran n benefits f from iti. it allows to portray itself as the protector and defender of the palestinian cause. >> qatar provides a a lot of humanitaririan support, thatat s would lilike to takeke credidit. giving the broad impression to israelis that hamas is focused on political activity. >> many experts say israel was focused on political activities of its own when it comeses to o hamas. >> netanyahuhu weirdly has prpreferred toto engagage with ththan with the paleststinian authoritity. >> we hahave some good reportit out of i israel ththat says tha bibi netanyahu said this is a way to ensure there will never be a palestinian state. we keep the palestinians divided. we slowly take more and more of the west bank.k. >> i asksked a senior r paleles. he told d meme, it is because netanyahu and the increasing far right coalition in israel want the dehuhumanize thehe palestin and ensusure they have a contntinuing narrativeve that i paleststinians arere not partne fofor peace. lookok at hamas. >> it's people like netanyahu whose hardline policies have strengthened hamas and given themem c credibilityty among palestininians. > the ideological commitmento hamas has s to be separateted d ththe only military powewer. auchblg, f for palestitinians so nonot supppport hamas i'd logic, theyey support h hamas resistat. >> t the p palestinians don't l at the c carnage and the death d the e constructition of theieir and evererything thehey knowow lolove and say, hey,y, we're blg hamas.s. they looook at this s th and se as p part and paparcel as ththe ununderlying p problem. israel's control of their lives, their denial of freedoms. >> no juanone wants to see civis killed. but why do people cry foul wheh it's i israelis. nobody s says anythihing. >> is it true that palestinians who live under israel's authority, do they live under separarate law? do they y face m more constraian their freeeedoms than n israeli? yes. palestinians are treated differently. >> before the october 7th attack, in 2023 alone, 227 palestinians were killed by israeli settlers and the israeli military. >> t the belief f was, if ththe efeffect of gazaza wasas a few rockets, w we could lilive with that. that was overturned on october 7th. when we returnrn -- >> the israeli army weren't able to communicate. >> this is a new level of terror. hamas has been trying to wipe out israel and israelis for three decades. but their october 7th attacks, at the gaza border,en israeli military bases, at a music festival, and on more than 20 vivillages andnd towns are unli anything its ever done before. >> this is a new level of terror. the number of dead. >> at least 1,400 people killed in israel. >> the number of wounded. >> 3, 00 so far. >> the number of those who were kidnapped, those are off the charts. >> 200 hostages, possibly more, were taken on what was the deadliest day for the jewish people since the holocaust. >> to put it in american terms, 1,400 israelis dead, is about 40,000 americans dying. the scale of the attack was staggering. so was the preparation. made clear by the documents found on the bodies of slain terrorists and shared with cnn by israeli officials. this document advises attackers to kill anyone posing a threat or causing a distraction, to keep captives away from arms or means of suicide. and to use them as canon fodder. hamas knew the exact number of harmed guards. this dococument says there were0 civilians and 10 soldiers. >> they knew about three or other entrances. they knew everything. where the generators are. >> it was a similar story next door to a military base. >> they killlled i thinknk 40 soldiers.. some of themem in ththeir sleep. whwhen they totook conontrol of militatary, they butcherered civililians. >> t they knew w what they w we doing. > if you lolook at the e orde have some of their written commands. they knew everything. >> they had knowledge about military targets, too. >> ten hamas p perpetratorors o five motorcycycles. ththey comome e on thehe secret inintelligence base. they know w where is t the back gate. it's unmananned. theyey explode t that gate.. theyey go in. they arere looking foror the bu where e the serverers are. ththey go leftft and right. the commanander said give me th mamap. and gigives him ththe mamap of secret i intelligencnce base.. >> w what happenened when ththe to where t they are orordered t? >> thihis is a b bunker ththat prototects the secreret service. the e bunker is s fortified.d. they kill some of the soldiers and they murdered them. >> being able to go in to where the communication servers were, caused a lot of chaos, where people in the israeli army weren't able to communicate for hours after ththe attack happen. >> israel wawas sickck with the of vanity anand undederestimati the enemy. >> d do you mean israeli's's chututzpah, not bebeing humble enenough to rerealize thatat thy of i israel is smamart, capable could do something this terrible? >> yeah. all of the above. >> once the attacks happen, details, brutal details, were spread across social media. a clear sign, hamas has grown and evolved, not just militarily, but also how they spread terror. >> one o of the mainin purposes this operaration, , was toto cr the videdeos the. they w were ordered d not just kikill and kididnap, but t to p ththe most h horrific acacts, a as youou can call a huhuman bei can dodo to anotheher one. documentnt that and d send it o to cenentral commamand of hamam. put this on social media. after the attack happened. >> an israeli some of the most horrific aprosatrosties occurre. >> was the body of a 14-year-old, 15-year-old.. headad choppeded off. i i don't want to geget into th details of what they havave don to peoplple in the houours unti they killed themem.. >> torturiring. all ofof it. >> m more than j just tortururi. the e evil. i'm writiting the bobook o on n. you cannot comprehend how someone can do these things. and you come and you see things that are so much worse. i think that what hamas did was to sentence this region to live on its sword for many, many generations, if not foforever. bebecause i don'n't know of f m israelisis, even t the most t l left wing that after this would sign a peace accord with any palestinians. they would just not trust them because of the atrocities. >> ahead -- >> there is no safe place in gaza anymore. israel's military dropped leaflets from the sky here earlier today warning the 1.1 million gazans living in north gaza to evacuate the area. >> there is no safe place in gaza anymore. >> mohammed, a british citizen who lives in manchester, england was on a family visit to gaza city when he was forced to evacuate south. >> we were told to come here because by the israeli army because it's supposedly safer for our safety. but it doesn't feel safer. there is bombing all around us every day, and truly, i don't -- i go to sleep, i don't know if i'll wake up. i go out. i don't know if i'll come back safe. foodod is runnnning out, runnint in the shopsps and we've not ha popower for morere than a a wee. ththe water susupply depenends power. >> for palestinians, all this movement out of their homes evokes memories of the 1948 expulsion. >> the nekba is something that permeates the psyche of palestinians, just like the holocaust permeates the psyche of israelis. people left their homes just like we did a week ago, and they thought it will be over. we'll be back in ten days. everything will be fine. and they've been dispossessed of their lands ever since. >> the humanitarian crisis in gaza seems to be growing worse by the hour. >> the dead are piling up. all of this only the beginning as those troops, hundreds of thousands of them, israeli troops amassing on that border. >> as the world watches and waits, the death toll is already staggering. this cnn graphic detailing fatales in the conflict over the past 15 years shows more palestinians have died each and every year, and the latest violence moves in the same direction. with profoundly more loss of life on the palestinian side since the horrific hamas attack on israel on october 7th. but the question remains, why did hamas strike now, likely knowing the devastation it would provoke in gaza. hamas spokesman name checked at the al aqsa mosque earlier this year as motivation for their attack. >> hamas has called this the storm of al aqsa, alalso k know temple mount, a place so holy to both jews and muslim here is in jerusalem. >> earlier this year israeli police raided the third holiest site in islam during the holy month of ramadan and the jewish passover. >> just israeli police stepping inside the mosque is considered incredibly provocative and aggressive. >> but many middle east experts say the timing of hamas' attack had more to do with the country that is home to mecca, the holiest of places in all of islam, saudi arabia. >> hamas was really concerned about the saudi moves to build ties with israel and the u.s. one concern was that saudi money would then bolsterer the paleststinian auauthority, its revival l and the e west bank.k. >> hamamas looksks at this worl an e emerging alliliance betweee moderate arabs and israel and decides we're going blow this whole thing up. >> if f the scalale of civilili casusualies in gaza is h high hf there isis p protracted conflic there e will be strong pressure within hezbollah and within iran to say we've got to wipe the coconflict.. >> w we've alrlready seen hezbo firing rocketsts. we've seseen uprisisings in thet bank.. >> the possisibility of escacaln is verery real. >> i f fear r israel i is s doi exacactly what h hamas wants, w is a an ininvasion, which mamay mamake hamas m more popular. >> nothingng w would be a a gre setback to hamasas than after r this an israeli-saudi normalization deal that is the strategic prize for israel.. >> diplolomatic and d political progreress in the mimiddle e eae often come in the aftermath of wars. >> when i was a young reporter, it would have been very difficult to imagine that the spanish government and basque extremists could sit down together and work things out. that happened. it would have been very difficult t to imaginene northe ireland being g at peaeace, andt happened.. i have this little ray of hope that it has hahappened elsewewh in thehe world. maybe somehow that can happen in gaza as well. >> in the days and weeks ahead, there is so much at stake here, and cnn will be here to cover it all. thanks for watching "the whole story." i'll see you next sunday. >> welcome to "the whole story." i'm anderson