Snowball the pig is a pragmatic leader, truly believing in the cause of the Animal Farm without directly seeking the overt power that Napoleon lusts for. His attitude towards war represents that pragmatism, showing that he believes their cause to be more important than human life. Boxer the horse, on the other hand, is a believer, but although he proves very powerful in battle, he regrets his actions:
"He is dead," said Boxer sorrowfully. "I had no intention of doing that. I forgot that I was wearing iron shoes. Who will believe that I did not do this on purpose?"
"No sentimentality, comrade!" cried Snowball from whose wounds the blood was still dripping. "War is war. The only good human being is a dead one."
"I have no wish to take life, not even human life," repeated Boxer, and his eyes were full of tears.
(Orwell, Animal Farm, george-orwell.org, emphasis mine)
Snowball wants to win at any costs, and feels no compassion for the humans he feels has oppressed them in labor. In Snowball's view, war is simply another obstacle that must be overcome in the most effective way possible. Boxer, however, wants to live in freedom with others, and sees life as more important than the Animal Farm cause. In Boxer's view, war is a last resort, and should never be taken lightly, since it results in death and pain on all sides.