If you're a big powerful country and you want to take over a smaller country, or a piece of it, you can simply occupy it with your army, a process known as annexation.
One of history's most famous examples of annexation was the German occupation of parts of Czechoslovakia in 1938, which became one of the causes of World War II. Although the most common use of annexation is in the sense of a political or military takeover of territory, it can also refer to less major acts of acquisition. If you manage to steal your colleague's much-coveted corner office at work, that too is an annexation.
n incorporation by joining or uniting
n the formal act of acquiring something (especially territory) by conquest or occupation
- Type of:
the act of contracting or assuming or acquiring possession of something