Why did old rivals britain and france form an alliance during world war i?

The correct answer to this open question is the following.

Old rivals, Britain and France, formed an alliance during World War I because they were afraid that Germany would invade and dominate Europe.

In those times full of conflicts in Europe, the French and Russians had already signed an alliance called Franco-Russian Alliance. Great Britain had to do the same in 1904 because the threat of Germany over Europe was real. It was called the Anglo-French Entente Cordiale and was a treaty of mutual cooperation. When British and Russians signed a treaty in 1907, the Triple Entente was formed and this Alliance fought the Triple Alliance of Germany, Italy, and Austria-Hungary in World War I.

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