Annexation is when one country takes control of another country's territory and makes it part of its own. When a nation annexes land, it's claiming that territory now belongs to them, usually by force or political pressure rather than through a fair agreement.

History is full of controversial annexations. In 1938, Nazi Germany annexed Austria, taking it over despite protests from other nations. Russia annexed Crimea from Ukraine in 2014, which most countries refused to recognize as legal. The United States annexed Texas in 1845 after it had been an independent republic, and later annexed Hawaii in 1898.

Annexation differs from conquest because the annexing country formally claims the territory as its own permanent possession, treating it like any other part of its nation. It's also different from colonization, where a powerful country controls distant territories but keeps them separate.

Just as a school might add an annex to create more classroom space, a country that annexes territory is adding that land to itself. But unlike adding rooms to a building, taking someone else's territory is almost always deeply unjust and harmful to the people living there.