It's defined in Article 42 of the Hague Regulations. Moving your army onto other land isn't occupation; it's invasion. Having your army assume AUTHORITY over that land changes it from an invader to an occupier. So it stands to reason that if moving your army ONTO land is not sufficient to begin an occupation, then redeploying them OFF that land isn't enough to end an occupation. What that army has to do is hand over its AUTHORITY over that land to someone else. Got it so far? Armies can even REMAIN on the land after the occupation ends, if the people who were handed that authority *ask* them to stay (e.g. Germany, post-45). Equally, an army can move to the periphery of the land (redeploy) and STILL be the occupying power over the land that is within, *if* it retains to itself the AUTHORITY to re-enter again and reimpose its will. THAT's Gaza, and THAT's Areas A & B in the WB. The IDF is *still* the occupying power over ALL that territory. Even today.
- 7:40 AM
from the article: Dreamland