During the Napoleonic Wars, British Army officers were allowed to resign their commission by either selling it or if they had not bought it then by formally resigning with no compensation. They were also allowed to go on half-pay. . . similar to retirement rather than just quitting. This happened often enough that it was not considered unusual in the memoirs and letters. Furthermore I have never seen a minimum amount of time that an officer had to serve before he left the Army.

How did other armies, especially the French Army, handle this?