It's easier said than done. Many people don't meet the military's requirements to join.

说起来容易做起来难。许多人不符合军队的入伍条件。

Early airplane design was largely dictated by military requirements, focusing on such things as maneuverability and firepower.

早期的飞机设计很大程度上取决于军事需求，重点关注机动性和火力等。