In what ways do you think the qualities Henry shows in battle would be useful in war today?
That depends on when you are referring to Henry's deeds in battle. Early in the book, Henry is so scared that he runs away from battle and then uses a logical argument to explain why he is so much more superior to the guys who stayed and fought.
"Nature had given him a sign. The squirrel, immediately upon recognizing danger, had taken to his legs without ado. He did not stand stolidly baring his furry belly to the missile, and die with an upward glance at the sympathetic heavens. On the contrary, he had fled as fast as his legs could carry him. . . . Nature . . . re-enforced his argument."
Self preservation was more important than bravery. I suppose that if all modern day soldiers did the same thing, there would be no one to fight wars. If no one is willing to fight them, then there isn't likely to be any wars. Sounds good.
By the end of the novel though, Henry has matured, and his battle attitude is much different. When the book begins, Henry wants to see battle in order to earn glory and fame for himself. As the story closes though, Henry has become wrapped up in something bigger than himself. He sees himself as a part of the military machine. He sees himself as a part of the cause. His self, isn't important any longer. He becomes selfless to bring glory to the cause and his country (symbolized by the flag he picks up in battle).
"Within him, as he hurled himself forward, was born a love, a despairing fondness for this flag which was near him. It was a creation of beauty and invulnerability. It was a goddess, radiant, that bended its form with an imperious gesture to him. It was a woman, red and white, hating and loving, that called him with the voice of his hopes. Because no harm could come to it he endowed it with power. He kept near, as if it could be a saver of lives, and an imploring cry went from his mind."
That selfless attitude and desire to be an effective part of the whole would be useful for modern day soldiers. It would be useful today for the same reasons it has always been useful in soldiers. They care less for themselves and more for their cause. They care less for themselves and more for the guy standing next to them. That concept was even spoken in the movie "Black Hawk Down." The following is Hoot's quote:
"When I go home people'll ask me, "Hey Hoot, why do you do it man? What, you some kinda war junkie?" You know what I'll say? I won't say a word. Why? They won't understand. They won't understand why we do it. They won't understand that it's about the men next to you, and that's it. That's all it is."
If all that soldiers worried about was self preservation, they would run away. If all they worried about was personal glory, they wouldn't follow orders and work well within a tactical unit. By being a selfless and brave portion of a larger machine, each soldier becomes a more effective member of that unit. That unit in turn gains effectiveness as a result. Henry clearly shows readers this by the end of the book.