War is a way to get what a group wants when no one will lend it. For example, if there were two tribes, one had food, the other didn't and the first refused to share, it would make sense to wage war otherwise they would starve. It comes from our basic instinct to survive. Furthermore, when people oppress or harm you unjustly, people have the right to retaliate. Without war the United States, and many other countries wouldn't exist. Without war, many parts of Europe would have stayed monarchial. War is sometimes justified.
Since the war has been started, we might have perception that the war is the last option to eliminate the threat or attack from another country's government. How ever, even we have been living in the world of war today but it seem that the war are fail to bring the peace. What we need is a peace not a war. If some people say that the war is purposed to stop the war it self but I dare to say that the war cannot stop the war. I'll give you one analogy. Lets say that we are attacking other country and we can guarantee that their last choice is to attack back and those process will never end until those country come together to a reconcilement. War cannot stop war but peace.
Never should one punch first. It was only until Guam, the Philippine Island, and other U.S. territories were attacked, and when Hitler declared war on America that was necessary. Now, if there is immediate threat of attack from another country's government, then war plans should be made. But a war on terrorist groups is a war on an idea. It will always exist.