- 5 star General. General of the Army. He'd be in his 60's. The US military does not use 5 star rank during peace time.
- 4 star- General. High political position or division commander, commander of entire armies.
- 3 star- Lieutenant General. Political position or command of divisions.
- 2 star - Brigadier General. Commander of "Commands", like all the troops in one certain country, like Germany or South America.
- 1 star General would hold low level political position or some kind of token command, not actually being in charge of anything. Could be in charge of a specific branch, like Cavalry or Infantry units. At least fifty years old, age goes up to 60's, from here on up, the age can pretty much be the same.
See full article at http://www.mitchpileggi.net/Deep_Background/resources/military/milrank.htm