Tom Swift and His War Tank

Tom Swift and His War Tank, Or, Doing His Bit for Uncle Sam:

When the United States joins in The Great War, it seems that everyone has war fever. A military base close to Shopton is training soldiers in the art of trench warfare, while pilots are learning aerial combat. Ned Newton has quit his job to sell liberty bonds full-time. Many of the young men have enlisted, or even hoping for the draft. Everyone seems to be doing their bit, except for Tom Swift, which raises many concerns that Tom is a slacker.

Tom does not let his country down; the reason he appears to be idle is that he has secretly been developing a new tank for use in combat. The project is so secret that Tom does not even let his close friends know, which causes the concerns being raised about Tom's patriotism. Even though the development is in secret, that does not stop German nationals from trying to steal his tank.