At the outbreak of the Second World War, on 1 September 1939, the Polish Air Force had 109 PZL P.11cs, 20 P.11as and 30 P.7as in combat units. A further 43 P.11c aircraft were in reserve or undergoing repairs. Only a third of P.11c were armed with four machine guns, the rest had only two, and even fewer had a radio. The P.11 were used in twelve escadrilles ("eskadra"), each with ten aircraft (two escadrilles constituted a squadron, in Polish: "dywizjon"). Two squadrons—four escadrilles—were in the Pursuit Brigade deployed around Warsaw, with the rest assigned to various armies. All of them took part in the 1939 defense of Poland. Apart from combat units, several P.11 aircraft, including a prototype P.11g, were used in improvised units at air bases.