I mean sure war helps bust the economy, it helps control the growth of population and it helps improve our technology, but are those the only reasons to consider war a "good thing"? in my opinion war is not a good thing but I have a debate to do and I have to say that war is a good thing...
No solider who has ever actually fought in a war would consider war to be a good thing. It has often been described as "An old man's war and a young man's fight." One of the reasons Harry Truman made such an excellent Commander-In-Chief during the Korean Conflict was that he refused to be swayed by MacArthur's recklessness in risking troops, Truman having witnessed and survived the trenches in World War I France as a youth. The aftereffects of conflict, however, have certainly yielded beneficial results, as others have noted. How unfortunate we must endure the former to achieve the latter.
For the purpose of your assignment, perhaps you can argue that going to war is sometimes an act of bravery (which is a good quality) since the homeland is threatened. President George Bush declared a war on terror, for instance, in order to prevent further attacks such as 9/11 upon the United States. This War on Terror has effected many protections against terrorism and has destroyed the regime of Sadam Hussain.
In World War II, for instance, the Polish, if they wished to keep their homeland, had no choice but to try to fight back against the Germans, who invaded their country. Likewise, when the U.S. was bombed by Japan [although Roosevelt knew about this bombing ahead of time and it could possibly have been averted], after this incident America had little choice but to wage war against Japan, who had so threatened it.
The violence of war is never the best choice, nor is it a "good" choice. However, sometimes it is the only choice. Take Hitler's Germany for example. Many US soldiers and their allies were lost in the war, but it was a situation of the greater good for the greater number. That is sometimes what war comes down to.
War can never be a "good" thing. It has been called by a variety of euphemisms, "failure of diplomacy," "diplomacy by other means," etc. Although it may lead to some improvements in technology and economic gain, the cost of human lives simply isn't worth it. At times, war is the only choice a nation may have to protect itself and its citizens, but that is the only time that it can be justified. To speak of it as a good thing is similar to calling homicide by self defense a good thing. It may prevent undesirable consequences, but any time human beings die at the hands of other human beings, there can be no "good" about it.
When you say "bust" the economy, do you mean that it hurts an economy? Not always true. WWII helped the US get out of the Great Depression.
As long as you're not talking about aggressive war, war can be a good thing. For example, the Civil War brought about an end to to the evil institution of slavery. World War II destroyed the Nazi regime in Germany.
This is not to say that it's good if war happens. It would have been better if those things had been destroyed without war. But war can certainly have good consequences at times.
In my opinion two people fighting is a bad thign much worse to have two countries fighting and even worse to have the world divided into groups that are fighting each other. it helps the economy, yes, but what will happen to the economy when we get to the point where so many people are dying, what about the pain that people go through to have their loved ones killed in action.