Previous: the hermits
There is a logical transition from the hermits to Cossacks , for while the hermits offer only a passive resistance, by trying to run away from an unjust society, the Cossacks are the peasants who run away to free land, and then actively resist the old society. You can say that they are a new version of "bandits ", only at a new, dialectical level.
N. Kostomarov in "The Russian History in Biographies", chapter about Ermak, says that the Cossack movement appeared during the Middle Ages and formed into a distinct group in XVI century. "Cossack" is a Tatar word, and it means "a free and a homeless bum". Cossacks have appeared in Russia from the class of people who were not taxed by the Czar, the tramps.
Cossacks were homeless and daring people. They were not afraid of danger, and found special beauty in overcoming it. They formed a kind of brotherhood among themselves.
A popular meaning of the word "Cossack" is a desire to escape the state, the slavery and the hardships of feudal society. Hence comes colonization of the East of Russia by Cossacks, in particular, colonization of Siberia by Ermak (see picture).
People saw in Cossacks a different kind of social system. The ideals of Cossacks were a complete personal freedom and equality. Hence, Cossacks originally formed amongst themselves a classless society. You can clearly see this in the painting of Repin "Cossacks Writing a Letter to the Turkish Sultan". There is a spirit of comradery and openness, daredevils and merry partying.
Cossacks settled on hard-to-reach islands for the purposes of defense. For example, the "Zaporozhtsi" settled behind the rapids of Dnieper on an island of Khortitsa. They also settled along other rivers of Russia and Ukraine, such as Don and Volga.
Some Cossacks were hired into Tsar's service. They were different from the "free" Cossacks (also known as "the thieves"). These last were hostile to the Tsar's government, offered shelter to the runaway feudal slaves and the dispossessed.
The free Cossacks attacked the merchants, the ambassadors, and ships that sailed along the rivers. They used special vessels for sailing, known as "chaika", meaning "seagull". A photo of a model of "chaika" from one of the Ukrainian museums is in the picture. They have used these boats even to sail accross the Black Sea to the gates of Constantinople. Notice, bundles of straw which the Cossacks tied around their boat to prevent it from sinking in a storm.
Here is a translation of a Cossack song which describes their adventures:
you the red sun,
over the abode of these good men
warm us up, the poor people,
the ragged men, the runaway people.
We are not thieves, and not robbers,
we are laborers of Stenka Razin.
As we wave an oar, we take over a ship.
As we wave a baton, we take over a caravan.
And as we take the caravan, we shake Moscow.
So, the Cossacks see themselves not as highwaymen, or plain robbers, but as "laborers of Stenka Razin", i.e. warriors for freedom.
When there was a pitched battle between government troops and the Cossacks, the former bested the latter due to their discipline, organization and military training. The government, periodically, sent out troops against the Cossacks, and the later hid themselves in caves and desserts.
Cossacks were characterized by boldness, enterprise, and fixity of purpose. For example, some of them could go far to the north, winter in caves and live on whatever food they found in taiga.
The spirit of Cossacks is best expressed by their letter to a Turkish sultan of XVII century. The Turkish sultan wrote a letter in which he extolled himself and said that the Cossacks should capitulate to him. To this, the Cossacks answered:
"You, sultan, are a Turkish devil, and a brother and a comrade to the devil, and a secretary to Lucifer himself. What kind of a damn knight are you, if you can not kill with your naked ass even a hedgehog? The devil shits, and your troops eat it up. Thou shall not, you son of bitch, have these Christian sons under your command; we're not afraid of your army, we are ready battle with you on land and sea, fuck your mother. You are a Babylonian cook, a Macedonian wheelwright, a Jerusalem brewer, an Alexandrian goat, a pig of the Greater and Smaller Egypt, an Armenian villain, a Tatar quiver, an executioner of Kamenets, a jester of the entire world and underworld, a viper's grandson and our dick's hook. You are a pig's face, a horse's ass, a low dog, a not baptized forehead, you son of bitch. That's what we, the Zaporozhtsi, told you, you shabby man. You are not good enough even to tend a Christian man's pigs. Here we end, for we don't know today's date and we don't have a calendar, but we have a moon in the sky, a year in the book, and the same day here as with you, and you can kiss us in the ass for this! Signed: Hetman Ivan Sirko together with the entire army of Zaporizhie".
Cossacks were jacks of all trades; they could easily prepare a military campaign on land, as on sea. Gogol writes: "There was no skill not known to the Cossack; he could squeeze wine, equip a carriage, grind the gunpowder, do the work of a smith, mechanic, and, on top of all that, party all night, drink and revel, as only a Russian could do - all this he could handle".
The Zaporozhian Sich, a Cossack fort on an island in Dnieper river, was in essence a communist society. Gogol writes that the Sich consisted of around 60 huts, "kurens", each of which was more like a separate, independent republic. No one possessed anything or held any personal property. Everything was handled by the Hetman of the hut, who was called "Dad". He handled money, dresses, all food, and even fuel; money was deposited with him for saving.
The government of Sich was direct democracy. The hetmans were appointed and overthrown by Cossacks themselves, of course under the influence of authoritative leaders. For example, in the book "Taras Bulba", we see the war party calling a meeting to overthrow the old hetman, "a dove", and appoint a new one, "a hawk".
If a Cossack stole something, even the smallest thing, this was considered a disgrace for the entire Cossack brotherhood; he was tied to a pole and a cudgel was laid down near it, and everyone had make a hit, until he was cudgeled to death. If a person owed money, he was tied to a gun with a chain, until someone paid his debt. A punishment for murder consisted of digging a grave, putting in it a murderer, on top of him a coffin with the body of the victim, and both were covered with soil.
Gogol depicts the Jews and the Poles as the main enemies of the Cossacks. The Jews were supposed to be bloodsuckers, for they were often the moneylenders. The hostility towards Poles comes from the fact they they were often the landlords who exploited the simple peasants. Hence, behind these national hostilities lie class contradictions.
The Cossacks are similar to the hermits and the monks in the following way: in the beginning, they opposed themselves to the state power, but later became of the pillars of the regime. Wikipedia writes that the Cossacks from the middle of XIX century till the October revolution of 1917 played the role of defenders of the Russian state power. During the Russian Civil War (1918-21) most of the Cossacks fought against the Bolsheviks.
During WWII, many Cossacks served with the Nazis, against the Red Army. They perceived this as an opportunity to take revenge for their defeat in the Civil War.
After the break up of the Soviet Union, we see nationalist, chauvinist forces using the Cossacks in the former republics of the Soviet Union as a fighting force. For example, Cossacks were used in the Transdniester republic fighting against Moldova. They are also used in the present by the Russian state fighting in the Donbass region against the official Ukraine.
Just like "mafia" was originally an association of armed Italian peasants to protect themselves from landlords, and later has become an unofficial thug for the capitalist state, so Cossacks have turned from representatives of the interests of poor peasants and people in general, into an armed forces for the interests of Kremlin bureaucracy.
That which was initially a revolutionary force has become its opposite. The same applies to revolutionary doctrines (e.g. Marxism), revolutionary organizations (e.g. the Russian Communist Party) and revolutionary states (e.g. the Soviet Russia). True revolutionaries need to discard the old and create the new.