Colonel! In today's Federation system, one only needed to advance one rank further and he or she would be a major general, a general!
God knows how many soldiers had toiled until their hair turned white on this rank, and how many more could only get to the rank of colonel right before they retired.
Generals, especially if they had risen from the ranks of real military attaches, could only get to this rank in the Federation by the age of forty, even if it was a very outstanding soldier.