regional dispute or another example of russian bullying, but at stake again are principles that made the world safer. >> reporter: russia claims it's threatened by aggression from the west and it's demanding security garn teas to diffuse this crisis, including a ban on ukraine joining n.a.t.o. that's something the u.s. says it will never agree to. ruia says has nons to invade ukraine, while some believe russia's president vladimir putin is playing a high stakes game of brinkmanship, ratcheting up --. in ukraine, they're prepared for a russian attack with bomb shelters like this one. they're already fighting are russian-backed rebellion in the country's east a conflict raging for over seven years that's killed more than 14,000 people. we were in the trenches this month with ukrainian forces trained and equipped by the u.s. they're in little doubt about