On 1 September 1939 German forces invaded Poland, triggering World War II. The Luftwaffe begun the invasion by bombing the undefended town of Wieluń. The Luftwaffe was an instrumental component of the Blitzkrieg battle plan. The Luftwaffe assigned two airfleets to the campaign. Albert Kesselring's "Luftflotte 1" was equipped with 807 aircraft, which was augmented by 92 Seaplanes of "Fliegerfuhrer der Seeluftstreitkrafte". Alexander Löhr's "Luftflotte 4" had 627 aircraft, augmented by 30 Slovak aircraft. A further 406 fighters were retained as part of home defence against potential Polish attack, while another 333 reconnaissance aircraft, under the command of "Kommandeur der Luftwaffe", were attached to the army.