 Stalin ordered shipbuilders to include false decks in the design of ships and while at sea, Soviet captains used deceptive flags and paint schemes to evade detection by the Nationalists.The USSR sent 2,000–3,000 military advisers to Spain; while the Soviet commitment of troops was fewer than 500 men at a time, Soviet volunteers often operated Soviet-made tanks and aircraft, particularly at the beginning of the war.The Spanish commander of every military unit on the Republican side was attended by a "Comissar Politico" of equal rank, who represented Moscow.