Here's The Real Reason Putin Can't Let Go Of South And East Ukraine
The output is vital to Vladimir Putin: 30% of Ukrainian military exports to Russia are unique and cannot currently be substituted by Russian production. And all military deliveries to Russia were suspended following the annexation of Crimea.
Bloomberg notes that Russia "would struggle without the 400 Ukraine-made engines it imports every year for its military helicopters or the $10 million it pays Ukraine to service its intercontinental ballistic missile system."
That's exactly why the Russian president would want to have these regions under Kremlin influence.
"Taking Ukraine's eastern and southern regions would be hugely beneficial for Russia from a military and economic point of view," Mikhail Barabanov, the editor-in-chief of the Moscow Defense Brief magazine, told Bloomberg. "Russia will have control of the very important and valuable defense companies and plants."
Separatists in the east already control the largest weapons cache in Europe: Over a million weapons including rifles, machine guns, and heavy weapons as well as millions of rounds of ammunition are stored in a facility built by the Soviet Union in the 1950s.
Furthermore, the port of Oktyabrsk in southwest Ukraine is critical for shipping Russian weapons around the world. This industry, run by "The Odessa Network," is not only economically valuable to Russia but also provides an important way for the Kremlin to exert power in proxy wars like Syria.
That is the primary reason Russia has an large investment in the rebels destabilizing south and east Ukraine: Putin's war machine relies on it.