The two 10p stamps are from 2008 History of Russian Cossacks issue.
It is after 1400 that the Cossacks emerge as an established and identifiable group in historical accounts. Rulers of Grand Duchy of Moscow and the Polish-Lithuanian Commonwealth employed Cossacks as mobile guards against Tatar raids from the south in the territories of the present-day southwestern Russia and southern Ukraine. Those early Cossacks seemed to have included a significant number of Tatar descendants judging from the records of their names. From the mid-15th century, the Cossacks are mostly mentioned with Russian and Ukrainian names.
Towards the end of the 15th century, Zaporozhian Cossacks had established a Cossack host in the "wild field" of Ukraine around the Dnipro River. In the 16th century, the Don Cossacks established another cossack host in the Don River basin. Others belonged to a Knyaz - slavic name for a royal nobility rank.
The Dnipro Cossacks of Ukraine formed the Zaporozhian Sich centered around the fortified Dnipro islands. Initially a vassal of Poland-Lithuania, the increasing social and religious pressure from the Commonwealth caused them to proclaim an independent Cossack Hetmanate, initiating by a rebellion under Bohdan Khmelnytsky in the mid-17th century. Afterwards, the Treaty of Pereyaslav with brought most of the Ukrainian Cossack state under Russian control for the next 300 years.
The Don Cossack Host, allied with the Tsardom of Russia, began a systematic conquest and colonisation of lands to secure her borders on the Volga, the whole of Siberia, the Ural and the Terek Rivers.
In the 18th century the Russian Empire's expansionist ambitions relied on ensuring the loyalty of Cossacks, which caused tension with their traditional independent lifestyle. This resulted in rebellions led by Stenka Razin, Kondraty Bulavin and Yemelyan Pugachev. In extreme cases, whole Hosts could be dissolved, as was the fate of the Zaporozhian Sich in 1775. By the end of the 18th century, Cossacks were transformed into a special social estate; they served as border guards on national and internal ethnic borders (as was in the case in the Caucasus War) and regularly supplied men to conflicts such as the numerous Russo-Turkish Wars. In return, they enjoyed vast social autonomy. This caused them to form a stereotypical portrayal of 19th century Russian Empire abroad and her government domestically.
During the Russian Civil War, Cossack regions became centers for the Anti-Bolshevik White movement, a portion of whom would form the White emigration. The Don and Kuban Cossacks even formed short-lived independent states in their respective territories. With the victory of the Red Army, the Cossack lands were subjected to famine, and suffered extensive repressions. During the Second World War, Cossacks fought for both the Soviet Union and for Nazi Germany, a choice which led to what has been called the 'Betrayal of Cossacks' by the Allied forces after the war, as the Soviet Union executed 'repatriated' Cossacks and again engaged in repressionary policies against their group. After the Collapse of the Soviet Union, the Cossack lifestyle and its ideas have made a return in Russia. Special Cossack units exist in the Russian Military, while Cossacks also have a parallel civil administration and police duties in their home territories that have become an integral part of contemporary society. There are Cossack organizations in Russia, Kazakhstan, Ukraine and other countries.