The Persian Cossack Brigade or Iranian Cossack Brigade was a Cossack-style elite cavalry unit formed in 1879 in Persia (modern Iran). It was modelled after the Caucasian Cossack regiments of the Imperial Russian Army, and until 1920, it was commanded by Russian officers, while its rank and file were composed of ethnic Caucasians and later on Persians as well. During much of their history they were the only functional, effective military unit of the Qajar Dynasty. Acting on occasion as kingmakers, this force played a pivotal role in modern Persian history during the Revolution of 1905–1911, the rise of Reza Shah, and the formation of the Pahlavi Dynasty.