Russia's troops don't just threaten Ukraine: They rely on it. too. More than50 factories in Ukraine's southern and eastern regions provide significant amounts of important hardware for Russia's military. Here's some examples :
Russia's heavy intercontinental ballistic missiles are designed and produced at Dneprpetrovsk.
The guidance systems for Russia's SS-25 and SS-19 strategic missiles are designed and produced in Kharkiv.
The Motor-Sich plant at Zaporizhzhya produces engines for Russian transport aircraft, military helicopters and some combat aircraft. Without the plant's facilities, Russia will have difficulty producing enough engines for its own demand.
Russia needs gears produce d in Mykolayiv for 60% of its navy's planned warships.
As far as raw materials are concerned
Zhovti Vody produces 20% of all natural uranium ore currently consumed by Russia's nuclear industry
Food supplies in Crimea which normally come from mainland Ukraine are under strain. Russia cannot easily meet this demand by land and sea from its own territory.
But Russia has seized all Ukraine's oil and gas facilities in the Sea of Azov. They have been taken over by Gazprom.
The Russian government's $15 billion agreement with former Ukrainian President Viktor Yanukovych aimed to further intertwine the two country's defence industries.
(Data from RUSI)