Leaders including Boris Johnson, Theresa May, and Volodymyr Zelensky discuss how they confronted Putin and manoeuvred to try and prevent his invasion of Ukraine.

Putin turns to the Middle East. After Gaddafi's overthrow in Libya, Putin shows just how far he's willing to go to keep his ally, President Assad of Syria, in power.

This first episode tells the story of how, when Putin first attacked Ukraine in 2014, Europe's leaders clashed over how to stop him. Amidst massive demonstrations demanding closer ties with the EU in Kyiv, Ukraine's president flees to Russia. Putin exploits the power vacuum to make the most audacious move of his presidency to date: sending troops into Crimea.

We go behind the scenes for the critical summits and fraught phone calls as the west tries to find a way to push back. The crisis heightens as the fighting spreads to Donbas in Eastern Ukraine and Malaysian Airlines flight MH17 is shot down. Key players including David Cameron, Francois Hollande, Jose Manuel Barroso and Ukraine's then-president Petro Poroshenko relive the EU's indecision and the all-night negotiations with the warring parties: a ceasefire is signed in Minsk, but Russian forces remain in Donbas.

Putin, meanwhile, appears more confident than ever. The lesson is clear, says French president Francois Hollande: 'When we do not punish at first, we are forced to punish more severely later.'