Dual Alliance: France and Russia formed the Dual Alliance for mutual aid against Germany.
Chantilly military conferences: The first proper allied military conference took place in Chantilly in July 1915, with further meetings following.
British support: Britain worked as the 'junior partner' on the Western Front, assisting the French, such as during the Battle of the Somme to relieve pressure at Verdun.
USA in war: The Allies had 65% of the world's manufacturing output compared to Germany's 19%.
Doullens: Allies agreed to appoint Foch as Generalissimo, improving cooperation significantly.