Article 1 of the April 11, 1899 Treaty of Paris states:

Spain relinquishes all claim of sovereignty over and title to Cuba. And as the island is, upon its evacuation by Spain, to be occupied by the United States, the United States will, so long as such occupation shall last, assume and discharge the obligations that may under international law result from the fact of its occupation, for the protection of life and property.

Notes: In fact, Cuba was already under US military occupation beginning July 17, 1898. Hence, Article 1 of this Treaty clearly shows that for a territorial cession, the period of time from the coming into force of the peace treaty up until the end of the military government of the (principal) occupying power is also called "military occupation."