After illegal overthrow of the President of Ukraine Victor Yanukovych.
Regions of southeastern Ukraine demanded the constitutional reform and federalization of the country. They battled for the right to speak their native language - Russian, which the illegal government from its first days wanted to forbid.
At first these were peace protests. But the Ukrainian police began to detain those who didn't agree with the policy of the illegal Ukrainian government which derived power after a military coup
The Ukrainian police and nazi groups started detaining, killing and crippling people who didn't agree with the position of the illegitimate government. Supporters of the state reforms and of amendments to the Constitution were called "separatists" (though the idea of federalization has nothing in common with separatism), terrorists and agents of the Kremlin.
The people of Donbass had no choice; they started protecting themselves as they could. When the weapon was used against them, the people of Donbass were compelled to take up arms too, to protect their relatives and families. The illegal government untied the so-called counter-terrorism operation which doomed more than one thousand innocent people, including women, old men and children. It was the last drop, so the new government, elected by the people of Donetsk and Lugansk areas, made the decision to separate from Ukraine stricken with lawlessness and chaos, in the only legal way - referendum. On May the referendum took place - with a stunning voter participation and not less stunning results -96, 2% of voters in Lugansk region and 89, 7% of voters in Donetsk supported separation from Ukraine.
What can be more legitimate, than the right for self-determination? than the desire of people to live a secure life, with strong and fair Constitution and within legal frameworks(in contrast to today's Ukraine where instead of freedom and democracy, permissiveness and anarchy reign! )
Now they entered the period when the civil war is imposed on us and the genocide of indigenous people is happening to the full extent today.
Involvement of external forces of the West in this conflict deserves separate consideration!