>> reporter: where rookie pilots are preparing for what officials here see as an increasingly urgent threat from china to invade, stripping taiwan of its democracy and autonomy. >> we can all foresee there might be war with china. that's what we are all preparing to do, like we're trying to fight. >> first lieutenant chang graduated from the u.s. air force academy. taiwan depends on the united states to survive. the island's 210,000 troops are no match for china's 2 million. >> i think of the obligation to make our sovereignty in tact. >> taiwanese defense officials tell nbc news a controversial trip by then speaker nancy pelosi a year ago was a turning point. >> america made a bedrock promise to always stand with