I see this decimation as an indicator of something far deeper that mear regional political differences (North vs South) that caused the entire senior officers corp of the United States Army in 1861 to resign almost to a man and join the Confederacy.

It is one of the few areas of the War for Southern Independence that has remained almost totally unexplored as to why this happened, because the cover story that they were all partisan southerners is so easy an answer to accept. Much has been made of Lee being offered the Command of the Union Army by Lincoln. But the fact of the matter is that by April 17th 1861, Lee and Phillip St George Cooke were the only actual Colonels or higher rank left to turn "out the lights" so to speak. Everyone else was gone.

These same men HAD TO BE INVOLVED in all the military planning that was going on in Washington DC in early 1861. Some of them had to have known the political purpose behind the events at Fort Sumter. The various plannings of military expeditions. And such things as the true purpose of the "Star of the West" Incident in January 1861, and the details of plans to reenforce Fort Sumter in April 1861. Lets not forget they would have also had some insight to the various peace delegations that had been sent by the southern States to talk with Lincoln.

Somethings convienced all of these men that resignation from the thing they had devoted their entire lifes work to defend and build, was the only thing their personal honor would allow them to do.

I wonder if any of these others such as Joe Johnson, Albert Sidney Johnston, Samuel Cooper et. al. left letters behind that gave any insight as to why they made the decisions that they did.