s-300s and other similar systems. you know how much depends on the battlefield on russia s ability to use aircraft. reporter: after zelenskyy s impassioned speech to congress, president biden announced a new security assistance package worth $800 million, including drones, antitank weapons, and 20 million rounds of ammunition. it includes 800 antiaircraft systems to make sure the ukrainian military can continue to stop the planes and helicopters that have been attacking their people and to defend their ukrainian airspace. reporter: despite being drastically outgunned, ukraine s forces have been putting up a tough fight. the country s ground troops, led my colonel general oleksandr sers ski, a veteran of the donbas region. meanwhile, chief commander of the armed forces, who is widely credited with reforming ukraine s military, vows to fight the russians to the last