As Germany invades Holland and Belgium, Winston Churchill becomes prime minister of Great Britain...

On May 10, 1940, the Nazis attacked the Netherlands, Belgium, and Luxembourg. From the article:

"As Germany invades Holland and Belgium, Winston Churchill becomes prime minister of Great Britain
On this day in 1940, Hitler begins his Western offensive with the radio code word “Danzig,” sending his forces into Holland and Belgium. On this same day, having lost the support of the Labour Party, British Prime Minister Neville Chamberlain resigns; Winston Churchill accedes to the office, becoming defense minister as well.

As British and French Allied forces attempted to meet the 136 German divisions breaking into Holland and Belgium on the ground, 2,500 German aircraft proceeded to bomb airfields in Belgium, Holland, France, and Luxembourg, and 16,000 German airborne troops parachuted into Rotterdam, Leiden, and The Hague. A hundred more German troops, employing air gliders, landed and seized the Belgian bridges across the Albert Canal. The Dutch army was defeated in five days. One day after the invasion of Belgium, the garrison at Fort Eben-Emael surrendered, outmanned and outgunned by the Germans.

The Dutch and Belgian governments immediately appealed to Britain for help. Neville Chamberlain pleaded to Parliament that a coalition government, of Liberals and Labour, would be necessary to generate support for a war effort, especially given the lethargy that infected Britain, still reeling from World War I. Labour demonstrated no support for Chamberlain, preferring Churchill, who they thought better able to prosecute a war. As one member of Parliament put it: “Winston—our hope—he may yet save civilization.” Great Britain had finally come to take the Nazi threat seriously.

Also on this day, in 1941, Rudolf Hess parachutes into Scotland in an attempt to negotiate a truce between Britain and Germany

On May 10, the day Hitler planned to invade Russia, and German bombs dropped on London in a spring “blitz,” Hess parachuted into Scotland, hoping to negotiate peace with Britain, in the person of the Duke of Hamilton, whom Hess claimed to have met at the 1936 Berlin Olympics. Such a peace would have prevented Germany from fighting on two fronts and greatly increased Hess’s own prestige within the Nazi regime.

He did, in fact, find peace—in the Tower of London, where the British imprisoned him, the last man ever to be held there under lock and key."