here are two such reviews:
A short synapses of what actually happened:
In 1940 after German went into France (after France & and the UK declared War on Germany) to secure the borders of Germany from a Soviet attack - the UK fought with the French and were pushed to Dunkirk and 400,000 mostly British troops were trapped by the English Channel. The Germans could have effectively wiped out UK military in a matter of hours!
Here is an article that is closer to the truth than the movie: