War & conquest.
It depends on the war.
Adolf Hitler did not invade Portugal during World War 2 because Spain stood in the way. In order to invade Portugal, Hitler would have needed to go through Spain. Spain would not allow that. Spain had far more to lose than to gain by entering the war. Spain had colonies in Africa that the Allied powers could conquer and Spain had very little to gain by entering the war. Both Portugal and Spain stayed out of the war. Spain helped Hitler and Portugal helped England as much as possible without actually participating in the fighting.
If you are asking about the American revolution Spain gained nothing in the war.
They gained independance,and land. The Treaty of Paris had a hand in stopping the Spanish American War. Spain gave America - Guam and Puerto Rico, and it allowed America to purchase the Philippines for $20,000,000. Cuba was freed from Spain.
In 1898.
The Spanish-American War was a conflict between America and Spain in 1898. America's intervention during the Cuban War of Independence and America's attacks on Spain's Pacific possessions led to this war.
The war of 1812 was started because of British ships attacking America trade ships. Putting trade at a stand still, destroying the economy. If America didnt go war then Americas economy would be worse then it would after the war. Although one hidden reason to go to war was to gain land such as Canada and Florida from Britain and Spain.
Parts of Spain.
Spain and America
WAR!
America eventually. But it wasn't one war, and it wasn't just America against Britain, it was France, Spain and America.