Why were U.S. submarine commanders replaced in wartime?

What happened to U.S. submarine captains when the fleet entered World War II?

Many officers seen as too cautious were promoted away, reassigned, or removed, while their executive officers took command.

The familiar claim is somewhat overstated, but the U.S. Navy did replace many submarine commanders judged too cautious for wartime operations. Some were reassigned, removed, or promoted away from sea command. Their executive officers then received commands and were expected to fight more aggressively. The example shows how quickly a service may have to correct peacetime personnel choices once combat exposes them.