The West Bank, Gaza, and East Jerusalem have been considered Occupied Palestinian Territories (OPT) since 1967, the occupation was a deliberate decision by Israel.
Israel is an Apartheid State by every international definition, with systematic discrimination and oppression of Palestinians. Divide and Conquer has been a tactic to separate Gaza from the West Bank, and also divide the West Bank into isolated enclaves.
On 1967:
Israel Claimed Its 1967 Land Conquests Weren’t Planned. Declassified Documents Reveal Otherwise: Haaretz and Forward