And the French and British tanks were reactions to trench warfare.
Trench warfare was around before WW1, most notably the Russo-Japanese War. From that conflict came the idea that the man with a bayonet would always get through. If that had been true then there would have no tanks because they would not have been necessary. However, because the bayonet approach along with pounding trench to mud failed the British and the French looked at alternatives.
Therefore, British and French tanks were a reaction to the failure of existing tactics to break through using just men and artillery. If they had been just a reaction to trench warfare they would have been rolled out earlier.