Yes, I think that the course of war is determined by one single battle, since one single battle can lead to an all out war. Too many times throughout history one single battle has lead to leaders wanting more, which then turns into an all out battle between the two sides.
The course of war isn't necessarily determined by one single battle, although momentum may shift from one side to the other during one particular encounter. The Battle of Gettysburg certainly helped break the Confederacy's army. However, battles leading up to Gettysburg helped embolden Robert E. Lee to try to invade the north. The same can be said of the Pacific Theater in World War II. The Battle of Midway was a turning point, but several naval battles occurred before that encounter in order to shape that event.
No. I do not believe the course of war determined by one single battle, because there are simply too many factors in a war to credit one battle for the final result. Other countries can get involved, or maybe some new information may surface that ends the conflict early. Or prematurely.
The course of a war is usually determined by large scale factors and not by a single battle. Often, the country with more people and resources will win no matter the results of any single battles. Although a single battle may decide the course of some wars, this case is rare.
No, the course of a war is not determined by one single battle. Instead, a myriad of factors goes in to determining who wins a war. For example, supplies, multiple battles, troop movements, and even weather can determine who ultimately emerges victorious. A single battle, while it may help cement a vitory, will never be its sole cause.