During the interbellum the Bulgarian military was not allowed to have active combat aircraft or naval vessels, and the army was reduced to about twenty thousand men in peacetime. In the early 1920s army officers participated in repressions during the Tsankov regime as part of paramilitary groups known as "shpitskomandi". In 1923 the army, along with "shpitskomandi" and Internal Macedonian Revolutionary Organization (IMRO) militia, violently suppressed the leftist September Uprising. Two years later Bulgarian troops stopped a short-lived Greek invasion of southwestern Bulgaria, known as the War of the Stray Dog. By the mid-1930s, the army had begun an expansion in violation of the Treaty of Neuilly-sur-Seine, following the rearmament pattern of Nazi Germany. During this period, the Bulgarian government procured combat aircraft from Germany and France, and light tanks from Italy.