Why did the lieutenant exclaim hot work! hot work! in chapter 17?

This would be his opinion of the way his regiment had fought; they were "hot." As you can see that definition hasn't changed much over the years.

"Hot work! Hot work!" cried the lieutenant deliriously. He walked up and down, restless and eager. Sometimes his voice could be heard in a wild, incomprehensible laugh."

Source(s): The Red Badge of Courage/ Chapter 17