<a href="https://en.wikipedia.org/wiki/World_War_II" id="mwjg" rel="mw:WikiLink" title="World War II">World War II</a>: The <a href="https://en.wikipedia.org/wiki/Battle_of_the_Heligoland_Bight_(1939)" id="mwjw" rel="mw:WikiLink" title="Battle of the Heligoland Bight (1939)">Battle of the Heligoland Bight</a>, the first major air battle of the war, takes place.