Even without launching a missile or creating a nuclear earthquake, the North Korean state certainly knows how to pull off a surprise. An event last Wednesday at the Chinese Embassy in Pyongyang, announced by the Chinese Foreign Ministry and North Korean state-run outlet KCNA, was a case in point.

The unexpected event was the celebration of the 57th anniversary of the Sino-North Korean Treaty of Friendship, Cooperation, and Mutual Assistance – a document first signed in 1961, which, like the suddenly-fragile NATO alliance, commits the signatories to aiding the other in the event of an external attack.