Thanks Robert for your precisions.
First in 1916 and second in 1918 are ideas of french historians!

I visited, with my wife, six years ago, the battlefield of the Somme.
We were in a house in the village of Courcelette (first battle of tanks!)
The battlefield was very impressive. We visited the Memorial of Thiepval, Vimy Ridge, Beaumont-Hamel and some museums.
I have a thought about Commonwealth soldiers who fought on this battlefield.
And I discovered we can play at Spearhead in the Great war !
Fabien