Although Katniss and Gale are close friends and are both against the Capitol, their views on war are quite different. Gale approaches war with a determined attitude and is willing to do whatever it takes to bring down the Capitol. In his opinion, the cause justifies committing big acts of violence against the opposition, such as imprisoning the wounded and killing Capitol soldiers. In contrast, Katniss does not support such violent actions. When she is making decisions, she strives to minimize casualties.
For example, consider how Gale suggests that they use avalanches to bury soldiers from the Capitol. Katniss does not support this idea when she hears it because she feels it is immoral. She is shocked when she realizes that Gale has "no interest in preserving the lives of those in the Nut." But in Gale’s opinion, this is acceptable because of the horrible actions that the Capitol has taken against their side. He has seen awful things, such as the firebombing in District 12, and this has made him determined to hurt people from the Capitol. He says that they should not give the Capitol soldiers a chance to surrender because they were not given a chance back in District 12. His response to the war is thus one based on anger and a desire for revenge, while Katniss's is based more on a desire to end it all and protect the innocent.