However, in July 1909, pro-Constitution forces marched from Iran's province of Azerbaijan to Tehran. They were able to capture Tehran, depose the Shah and re-establish the constitution. Colonel Liakhov and his forces served the Shah until July 1909, when the Shah abdicated and fled to Russia, resulting in the surrender of Liakhov and the Persian Cossack Brigade. Liakhov was pardoned by the Constitutional leaders probably for the fear of a Russian attack and was sent back to Saint Petersburg, where he would be dismissed soon after to serve in the Caucasus campaign of the First World War.