the city's fall to isis in may, an embarrassing defeat that had defense secretary carter questioning their resolve. >> they failed to fight. they withdrew from the site. >> reporter: week ago, carter urged iraq's prime minister to move north toward mosul. iraq's second-largest city where isis leader abu bakr al baghdadh proclaimed the caliphate more than a year ago. >> we do want to help you build on your success in ramadi, to move toward mosul. >> reporter: after a recent string of defeats, north of baghdad, and sinjar mountain, al baghdadi warned in a new recording that despite the setbacks, isis remains strong, promising an epic final battle. [ explosions ] >> reporter: on monday, iraqi prime minister al badhi tweeted with confidence that the iraqis are going to liberate mosul.