Persia declared formal neutrality in World War 1 but in reality they were forced to help the Allies because of the Anglo-Russian Treaty of 1907 where Russia and the UK spilt Persia in two spheres of influence. The northern half was the Russian Sphere and the southern was British. At the outbreak of WW1 the Ottomans wanted to cut off Russian access to Persia and the Caspian Sea and make a way to British India. They would continue fighting until the end of the war.