A pro Nazi coup by Iraqi officers who were seeking full, rather than the then partial, independence from the UK took place. The plotters were in contact with the Germans and had calculated that World War Two could bring this about. Instead, it brought about a direct British intervention that made short work of the coup.
The Germans and Italians did attempt to aid the insurrectionist by supplying aircraft. Vichy France allowed the use of its airfields in Syria, which would bring about the British intervention in Syria terminating their rule.
The plotters, termed the "Golden Circle" had formed in the 1930s and had been working towards this goal since that time. Supported by the German ambassador in Iraq, their goal was to overthrow the British supported monarchy, end British influence in the country, and form a fascist state.
While the coup was a catastrophic failure for those participating in it, it's worth noting that in some ways it echoes to this day. Fascism was proving to be popular in Middle Eastern quarters and it would reemerge as the Baath Party, a pan Arab fascist movement which still rules Syria and which did rule Iraq under Saddam Hussein.
More on that, and the ongoing British advance in the desert, can be read about here:
Today in World War II History—April 1, 1941
The Germans, it should be noted, would find their air intervention in Iraq ineffective and Vichy's decision to allow the Germans and Italians to use their airfields would end, forever, French rule in Syria. Syrian airfields were already under attack by the UK at the time, so France's decision was not as bold as it might seem, given the circumstances. Nonetheless France was entering the quasi belligerent stage.
British Commonwealth forces took the capitol of Eritrea on this day.
The Germans did seem to be reversing Axis fortunes in North Africa, however.
Workers at Ford Motors went on strike.
New York hit 60F for the first time that year, the fifth latest such date since records started to be kept, at that time, and now the seventh.