Britain snubbed military alliance with Russia in 1939.

 

Winston Churchill

Churchill wasn't always seen as a great British leader. He was blamed for British failures at Gallipoli during WWI and was thought by many British people to be a warmonger before the outbreak of war with Germany in September 1939.

Britain's greatest defence is that it's an island surrounded by seas that are often perilous, which makes any invasion by sea difficult, but not impossible. It deterred both Napoleon and Hitler. Hitler knew that if Germany tried to invade England by sea, it would incur great losses in an encounter with the Royal Navy.

Lord Halifax and others wanted to negotiate with Hitler but Churchill opposed this and said he would never negotiate with a Hitler-led German government. Britain could not have beaten Germany alone without the help of the Americans. The German invasion of Russia was also a turning point. Some historians do argue that Britain delayed opening up a second front so the Russians would have to do most of the fighting. Stalin did offer Britain and France a military alliance before it entered into a pact with Germany but their proposals were snubbed. Anti-communist feelings were widespread among British conservatives and the western democracies were happy to see Russia and Germany at war with one another.

The British government did send Admiral Regional Drax on a mission to Moscow in August 1939 to discuss an alliance, but the Russians soon realised that Drax was not a government minister and had no authorisation to agree to anything. The Russians also realised that Britain could contribute very little to an alliance in terms of military hardware and equipment.