 Complete the following phrase:  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 