Mutual defense pact between North Korea and Russia raises new questions, but it's far from unique

A new mutual-defense pact signed by Russian President Vladimir Putin and North Korean leader Kim Jong Un commits each country to come to the other's aid if attacked.

Just what the threshold for such assistance would be is currently unclear — maybe deliberately so, to deter other countries from putting it to the test. Putin initially told Russian media that the partnership provides for “mutual assistance in the event of aggression against one of the parties,” while North Korea's state-run Korean Central News Agency later reported that the pact's Article 4 called for assistance “in the event that either of the parties is invaded and pushed into a state of war."

If the pact is triggered, the countries' obligations are also vague, with KCNA reporting that if one is attacked the other must deploy “all means at its disposal without delay” to provide “military and other assistance.”

Experts note that the language is almost identical to that of a previous mutual defense pact from 1961 between the Soviet Union and North Korea, which was never put to the test.

Such pacts are not uncommon and are rarely invoked, while often being touted as a means of deterring aggression, though the agreement between the two unpredictable and autocratic leaders of nuclear nations immediately raised concerns globally.

The United States has many similar treaty obligations with other Asian nations, not to mention through NATO's Article 5 provision, which says that an attack on a member of the alliance is to be considered an attack against all of its members. The only time NATO's Article 5 has been invoked has been to come to the defense of the U.S. after the Sept. 11, 2001, attacks.

Russia also has mutual defense pacts with several post-Soviet