Ukraine and Russia's European Empire

What prompted the Tsars to create a Russian Empire that colonised Ukraine, eastern Poland, the Baltic States and other lands in Eastern Europe? Was Moscow seeking greater security or fulfilling a sense of religious mission, or was Russia's western expansion simply naked nationalism and greed? 

In this edition of Black's History Week, Professor Jeremy Black discusses with The Critic's deputy editor, Graham Stewart,  the lessons that this history holds today as Putin's forces threaten Ukraine.