Politics were a major factor in how and from whom North Korea received much of its military assistance - and why they have kept 'obsolete' types that others no longer operate.

The Korean War saw both the Soviet Union and Communist China come to North Korea's aid, with both providing them with military equipment.

The ideological fracture between the Soviet Union and China at the beginning of the 1960s saw North Korea side with China, with its relationships with the Soviet Union deteriorating considerably.

This made China its main military provider until 1981, when the North Korean relationship with China deteriorated considerably, following China's closer ties with the West (Deng Xiaoping 'Open Door' policies). North Korea moved closer with the Soviet Union, who at that point became their main provider of military equipment - a situation that lasted until 1991 and the disbanding of the Soviet Union.

Already isolated, things turned worse for North Korea following its economic collapse starting in the second half of the 1980s, culminating in the major famines in the second half of the 1990s - meaning the country simply had no money to modernise its military.

Following its development of nuclear weapons in the early 2000s, an international embargo was put in place against North Korea, which made it only more difficult to acquire replacements for its increasingly obsolete air force. It's only in the recent two years that things appear to have started changing - North Korea's willingness to help out Russia in its campaign against Ukraine seems to come with a promise to provide North Korea with more modern equipment, such as MiG-29s and Sukhoi Su-27s.

In short, they received the bulk of their aircraft from China and the Soviet Union between 1950 and 1981; they received slightly more modern aircraft (MiG-23s, first-generation MiG-29s and Sukhoi Su-25s) in small quantities from the Soviet Union between 1984 and 1991; and... well, that's it. With barely 35 'modern' MiG-29s and 34 'modern' Su-25s; and 56 'sightly more obsolete' MiG-23s; they've pretty much been forced to keep their older aircraft in service, as retiring them would represent a serious reduction of their air force. Hence they still have about 30 Shenyang F-7s (MiG-21)s; around 20 Sukhoi Su-7s; around 100 Shenyang F-6s (MiG-19s); some 80 Harbin H-5s (Il-28); around 100 Shenyang F-5s (MiG-17s); and somewhere between 30 and 100 MiG-15s (single- and two-seat variants).