North Korea sent more than 1,000 soldiers to North Vietnam between 1966 and 1972, including hundreds of pilots who flew MiG-17s in combat, according to a book published in 2017 by the South Korean defence ministry's Institute for Military History.
The North's air force shot down at least 26 U.S. planes and lost 14 of its own personnel from 1967 to 1969, a retired Vietnamese air force official told the country's People's Police newspaper.
Another team of North Korean psychological warfare specialists was also deployed to support North Vietnam's propaganda and abduction operations targeting South Korean troops in South Vietnam, while dozens of Vietnamese guerrillas were trained in North Korea, the South Korean book said.
But relations have cooled since Vietnam began embracing the West, launching political and economic reforms in the late 1980s and establishing diplomatic ties with South Korea in 1992.
During the Yom Kippur War in 1973, North Korea sent a group of about 1,500 military advisers and some 40 air force personnel to Egypt, following a military assistance pact between its late leader Kim Il Sung and Egypt's Hosni Mubarak, said Niu Song, a professor at Shanghai International Studies University.
North Korea fostered military exchanges with Libya under Muammar Gaddafi, clinching a 10-year alliance treaty in 1982, which called for either to render military aid if the other was attacked and threatened by a third country.
A declassified 1982 CIA cable said Pyongyang might have been seeking to turn Libya into an "out-of-country storehouse" for its military, citing past reports about North Korean pilots and training on MiG-23s there, while laying the groundwork to acquire nuclear weapons.
Syria is a longtime friend of North Korea, working jointly on missiles and chemical weapons. The North also built a plutonium reactor there, destroyed by an Israeli strike in 2007. In 2013, Israeli media said several North Korean helicopter pilots and artillery officers were operating in Syria, though Pyongyang's state news agency denied providing military aid. In 2016, Russia's TASS state news agency said two North Korean military units were fighting in Syria's civil war for President Bashar al-Assad.
Both subject to U.N. sanctions, North Korea and Iran have also been suspected of co-operating on nuclear and ballistic missile programmes, exchanging technical expertise and components. In 2015, an exiled Iranian dissident group that exposed the country's Natanz nuclear facility in 2002, said a delegation of seven North Korean nuclear and missile experts visited a military site near Tehran, their third such exchange that year. U.N. monitors in 2021 revealed that the countries had resumed co-operation to develop long-range missiles, transferring critical parts. North Korea has also been accused of supplying weapons to Iran's proxies, including Hamas, whose fighters were seen using its grenade launchers in their 2023 attack on Israel, which was denied by Pyongyang.
North Korea has had longstanding ties with authoritarian regimes in Zimbabwe, Uganda and elsewhere in Africa since the Cold War era, engaging in arms sales and military training. In 2011, a South Korean lawmaker said North Korea had more than 100 rounds of arms sales talks between 1999 and 2008 with countries such as Angola, Congo, Libya, Tanzania and Uganda, citing confidential government data. The transactions aimed at earning dollars to buy newer weapons and parts from Russia by selling old, cheap conventional ones in Africa, according to the Institute for National Security Strategy of South Korea's national intelligence agency. But North Korea's relations with many African partners have waned over the past decade since facing tighter U.N. sanctions, with Botswana severing diplomatic ties in 2015 and Uganda and Ethiopia halting security exchanges in 2016.