pact

But throughout the war, both sides have taken care to avoid turning the conflict into a direct battle between Russia and NATO, whose 32 member nations, including the United States, have a mutual-defense pact.

But there is no doubt that the pair have stepped up cooperation after signing a security pact in June to help each other in the event of "aggression" against either country.

Back during the Cold War, the Kremlin blocked its Warsaw Pact allies from developing or obtaining nuclear materials—it even confiscated some of those allies’ uranium mines.

The UK already has a defence pact with France – the Lancaster House Treaty which was signed in 2010 by David Cameron and Nicholas Sarkozy – but this is the first with Germany.

Moscow and Pyongyang have stepped up cooperation after their leaders Vladimir Putin and Kim Jong Un signed a security pact in June, will pledges that their countries will help each other in the event of "aggression" against either country.