Control of Ukraine would give the Russian navy a wider coastline to operate from.
Ukrainian border guards stand at a checkpoint from territory controlled by Russia-backed separatists to the territory controlled by Ukrainian forces in Novotroitske. (AP)
Politics and ideological angst
Russian President Vladimir Putin's fixation with the Soviet era when Ukraine was part of the communist USSR. The country gained independence in 1991 after the fall of the USSR. Other Eastern European states under the erstwhile Soviet Union also went their separate ways.
Ethnicity and religion
Russians and Ukrainian share the same ethnicity - both are Slavs. Both also belong to the Eastern Orthodox Christian denomination.
Naval expansion
Better access to warmer Black Sea ports like Odessa. Russia already controls Crimea for its Black Sea fleet operations. Control of Ukraine would give the Russian navy a wider coastline to operate from.
Perceived Nato threat
Russian President Putin believes Nato, the Western military bloc former after WW2, plans to expand East into Europe. Ukraine was to join Nato at a later date. Nato missiles in Poland are also a concern.
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