Vladimir Putin sent a letter to Kim Jong Un to say that their two nations will “expand the comprehensive and constructive bilateral relations with common efforts,” North Korean state media revealed Monday. The Russian president added that closer ties would be in both countries’ interests and that it would help bolster the stability of the Korean Peninsula. Kim replied with a letter of his own, arguing that “strategic and tactical cooperation, support and solidarity” between their nations had reached a new level to help resist threats from common hostile forces. While state media didn’t specify which hostile forces Kim was referring to, North Korean media has used the term to euphemistically refer to the U.S. and its Western allies in the past. The tyrants’ pen-pal relationship comes after Ukraine severed diplomatic ties with North Korea after Pyongyang officially recognized two Russia-backed breakaway republics in eastern Ukraine as independent countries, with officials even offering to send North Korean workers to rebuild damaged infrastructure in the regions.