'Thesis' was a British air operation against German targets in Crete (23 July 1943).

The undertaking was part of the Allied effort to pin German and Italian forces in the eastern basin of the Mediterranean Sea and at the same time to boost the morale of the island’s Greek inhabitants, and served also to help persuade the Axis command in the period just before the launch of 'Husky' (i) against Sicily that Allied forces might be preparing an invasion in the eastern Mediterranean, on Crete or some of the island groups of the Aegean Sea, or even in Greece. The effect of these and other diversionary measures was that more German forces were moved into mainland Greece as well as into Crete, Rhodes and other Greek islands.