In the case of all wars, it is sometimes worth considering the aims for which the war was originally declared (or the surprise attack originally launched, or whatever). Sometimes, it is possible that a limited objective can be achieved without all sorts of ramifications and unintended factors getting in the way. (Example: the Falkland Islands War).

More often, a confused original situation combined with half-hearted statement of intentions produce all sorts of surprises, or an inevitable drift into an unwanted situation.

The Anglo-American War of 1812 is one I have studied (and visited some of the Battlefields). The Americans declared war against Britain on the grounds against some British Orders-in-Council aimed at blockading Napoleon's Europe hid American commerce hard, and high-handed impressment of seamen into the RN from American merchant ships. Within a couple of months, the offending Orders-in-Council had been rescinded, and American seamen could obviously no longer be taken into the RN (though as prisoners-of-war or interned belligerents, their situation wasn't immediately much better). But it took another two and a half years before Britain and America stopped fighting.

The Americans did win one important strategic victory. Tecumseh's confederation of Indian tribes naturally allied itself with the British and depended on them for weapons and supplies. The Americans broke the confederation, and killed Tecumseh himself. However, they would have achieved this sooner or later, with or without the War of 1812.

Other than some of the Indian peoples, the only losers of the War of 1812 were the unfortunate inhabitants of Washington, York (modern-day Toronto) and several other communities around Chesapeake Bay, the Niagara River and in modern-day Ontario, who lost their homes and other property, and sometimes suffered worse indignities and mistreatment.