"One [of the wounded] was swearing that he had been shot in the arm through the commanding general's ________ of the army."

The word you're looking for is 'mismanagement'. Here's the quote at length:

"One was swearing that he had been shot in the arm through the commanding general's mismanagement of the army. One was marching with an air imitative of some sublime drum major. Upon his features was an unholy mixture of merriment and agony."