 Although France maintained roughly 300,000 troops in Iberia during the Peninsular War, the vast majority were tied down to garrison duty and to intelligence operations.The French were never able to concentrate all of their forces effectively, prolonging the war until events elsewhere in Europe finally turned the tide in favour of the Allies.After the invasion of Russia in 1812, the number of French troops in Spain vastly declined as Napoleon needed reinforcements to conserve his strategic position in Europe.