Bigfun, The French soldiers they were fighting were Vichy French.
Have a look here.
Vichy France - Wikipedia, the free encyclopedia

North Africa had to be cleared of Germans as well as the rest of the Med as it would then free up shipping.
The quickest way from the UK to India , Burma and down to Australia is through the Med & down the Suez Canal on onwards.
Until the Med was clear of Axis Forces supply convoys had to take the long way round via South Africa .
Once the Med was free the shipping saved could then be used to get supplies across the Atlantic quicker.
Well that's how I see it.

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