Russian President Vladimir Putin has signed a new military doctrine that says NATO is one between for in of over to under with Russia's biggest dangers. NATO (the North Atlantic Treaty Organization) is a defence treaty that started between for in of over to under with 1949. It consists between for in of over to under with North American and European countries who guarantee to act if any member state is threatened militarily. Tensions between for in of over to under with Russia and NATO have existed since the end between for in of over to under with WWII. The rival, Russian-led Warsaw Pact started between for in of over to under with 1955 and led between for in of over to under with the Cold War between the East and West intensifying. Strained relations have surfaced once again between for in of over to under with former Russian ally Ukraine making fresh steps to join NATO. Russia accused NATO this week between for in of over to under with turning Ukraine into a "frontline between for in of over to under with confrontation". The new doctrine has stated that between for in of over to under with the first time, Russia would use conventional weapons "as part between for in of over to under with strategic deterrent measures" if it sees its territory is between for in of over to under with threat. A NATO spokeswoman said the organization was complying between for in of over to under with international law between for in of over to under with Ukraine and was not threatening Russia between for in of over to under with any way. She said: "Should Ukraine decide to apply between for in of over to under with NATO membership, NATO will assess its readiness to join the alliance between for in of over to under with the same way as between for in of over to under with any candidate. This is an issue between for in of over to under with NATO and the individual countries aspiring to membership." She added: "It is Russia's actions…in Ukraine which are breaking international law and undermining European security."