Russia can nuke Ukraine off the map. But those Russian nukes can’t fly without Ukrainian spare parts.

While Russia only obtains 4.4 percent of its total imports from Ukraine, around 30 percent of Ukrainian military exports to Russia “are unique and cannot currently be substituted by Russian production,” according to the Royal United Services Institute, a British think tank.

Now Russia is about to find out why it’s better to have Ukraine as a friend than as an enemy. Ukroboronprom, the Ukrainian state-owned conglomerate that controls military production, has frozen arms sales to Russia.

This is bad news for Russia’s Strategic Rocket Forces. Its SS-18 ICBMs are designed, manufactured and maintained by Ukraine’s state-owned Yuzhmash enterprise in Dnepropetrovsk. The SS-19 and SS-25 ICBMs are designed and produced in Russia, but their guidance systems come from the Khartron company in Kharkov.

These three types account for more than 80 percent of the missiles in Russia’s rocket forces.

“In addition, some 20 per cent of the natural uranium currently consumed by Russia’s nuclear industry, both for civilian and military purposes, comes from Zholti Vody in Ukraine,” RUSI reported.

Russian military dependence on Ukraine also applies to conventional arms. “Russia requires Ukrainian-produced gears for 60 percent of the surface combatants planned for its navy,” RUSI pointed out.

Ukraine’s Motor-Sich plant manufactures jet engines for Russian transport aircraft, engines for all Russian combat and transport helicopters and auxiliary power units for many types of aircraft and helicopters. Ukraine also makes auxiliary equipment, such as hydraulics and drogue parachutes, for advanced Russian fighters such as the Su-27, Su-30 and Su-35.

Ditto for the missiles carried by those fighters. Ukrainian companies manufacture the R-27 air-to-air missile as well as seekers for the R-73.

When Ukraine was part of the Soviet Union and comprised a large part of Soviet heavy industry, it made sense for key defense components to be manufactured there. But Ukraine declared independence in 1991. Why is Russia still dependent upon another country for its most sensitive military equipment?

“This is due to the fact that lots of the Strategic Rocket Forces missiles and their components were produced during the Soviet time by Ukrainian-based plants,” Igor Sutyagin, the RUSI researcher who co-authored the Ukraine report, told War is Boring. “It was impossible to build other plants which would produce the same products.”

Not that Russia hasn’t made some effort to foster domestic production. For example, Moscow has tried to reduce dependence on Motor-Sich for helicopter engines. Yet it still cannot manufacture enough engines domestically to either meet its own rearmament program or meet export orders for helicopters, according to RUSI.

What about existing stockpiles of spare parts? “It is important not to overestimate the amount of spare parts [in reserve], and not to underestimate the actual need Russia has in such parts,” Sutyagin told War is Boring. “They are far too numerous to buy and keep in storage under normal conditions.”

And even if the spare parts were there, Russia still needs Ukrainian specialists to service its nuclear missiles.