The Argentinean Invasion of Brazil in March of 1980 is regarded as one of the critical episodes of the lengthy Brazilian War. The invasion is generally regarded as being caused by the undeclared war having been fought for months along the border between the two countries and the shooting down of Argentinean airplanes by Brazilian government forces throughout 1978 and 1979, including a commercial airliner on February 27, 1980. The rapid mobilization and assault against Brazilian forces amassed against the border occurred starting in the middle of the night and was followed that afternoon by a formal declaration of war by Argentinean President Isabel Perón.