It is an ironic fact that much of the equipment used by the Russian troops in Crimea, and those maneuvering on Ukraine's border, is produced by Kyiv's military industry.
The equipment includes the motors that keep all of Russia's combat helicopters flying and many of the engines that power Russian naval ships. It also includes about half of the air-to-air missiles carried by Russian fighter planes.
But the sight of Ukrainian-produced hardware now pointed belligerently at Kyiv is not simply incongruous. It also underlines how much Russia's military risks shooting itself in the foot if rising tensions cause the two countries to break ties. Conversely, it could also lead Russia to seek to control Ukraine regardless of the costs.
In a recent article
, RFE/RL Russian Service's military correspondent Vladimir Voronov argues that severing ties with Ukraine would have a far more dramatic impact on Russia's defense program than any Western sanctions restricting sales of Western military hardware.
Voronov notes that the two countries' military industrial complexes are so integrated that any end to cooperation with Ukraine would seriously jeopardize the Russian army's ambitious modernization program.
The integration of the Russian and Ukrainian military industries dates to the Soviet Union, when Moscow planners deliberately located key manufacturing plants in various Soviet republics to strengthen national unity. Since the collapse of the U.S.S.R., Moscow has sought to create its own entirely domestic military industry in a declared policy of self-reliance.
But Russia's self-reliance program remains far from complete.
Moscow envisions spending at least 20 trillion rubles ($563 billion) from 2011 to 2020 on upgrading its military, including updating its strategic nuclear forces, expanding its navy, and modernizing its air and ground forces.
Yet the design bureaus and enterprises meant to do the work are so overwhelmed that Deputy Prime Minister Dmitry Rogozin said as recently as December that they were "overworked" and "do not have time to do what the Defense Ministry orders."
Igor Sutyagin, a research fellow for Russian studies at Royal United Services Institute in London, cites engines for new combat and transport helicopters as one example.
"Russia needs approximately 3,000 of them and has managed to build just one fully Russian equivalent," he says. "It is currently planning to produce approximately 50 a year, while it is going to need approximately 3,000 engines for its helicopters in a matter of two or three years."
The Ukrainian facilities which are most important for Russia's military are Motor Sich in Zaporizhzhya, which produces helicopter engines, Yuzhmash in Dnipropetrovsk, which manufactures rockets and missiles, and the Russian company Antonov's plant in Kyiv, which makes planes.
Some of the most important ties between the two countries' military industries concern Russia's strategic nuclear forces.
Most of Russia warheads are delivered by rockets which were entirely produced or designed by factories in Soviet-era Ukraine or contain key components from them.
In his article for RFE/RL's Russian Service, Voronov notes
that more than half of the components of ground-based intercontinental ballistic missiles (ICBMs) can be traced back to Ukraine and that these rockets carry over 80 percent of Russia's warheads.
The essential components include targeting and control systems, most importantly for Russia's keystone ICBM, the RS-20B Voyevoda, known by NATO as the SS-18 Satan. The guidance system was produced in Kharkiv at a factory known as "Elektropribor" in the Soviet era and as "Khatron" today.
Ukrainian specialists continue to carry out regular inspections of Russia's strategic missiles in order to certify them for service.
Voronov writes that the technical certification is particularly important as even the newest Satan missiles are almost 25 years old and nearing the end of their service lifetime. Moscow needs to keep them operable until 2018 - 2020, when a new Russian-built ICBM, the Sarmat, is due to take their place.
Military experts say that Russia itself could carry out the inspections work on the missiles but that losing the cooperation of Ukrainian factories would be a setback.
The former chief of staff of the Strategic Missile Forces, Viktor Esin, recently acknowledged that "there would be difficulties, because the documentation is in Ukraine, but the problem is solvable."
Such public discussion of the risks the Russian military runs is rare. But it is a sign that at least some in Moscow are weighing what further costs interference in Ukraine could bring Russia beyond Western sanctions.
So far, Moscow seems to be betting that even if relations with Kyiv sour further, cooperation between their military industries will be one of the last relationships to be abandoned.
According to Sutyagin, the reason is not just the strategic importance of the relationship to Russia but also its commercial importance to Ukraine.
"The Ukrainian military industry heavily depends on Russia because Russia represents 30 percent of Ukrainian exports and these are the most valuable exports because these are the most expensive," he says. "It would be extremely difficult for Motor Sich which produces the helicopter and jet engines to find a European market because [the market] is already dense and these engines do not perfectly fit the European and world standards, quality standards, noise standards, pollution standards."
Still, the very tightness of the military industrial partnership between Russia and Ukraine makes it an unpredictable factor in the current crisis.
The desire of both sides to maintain their military trade could help put a brake on escalating tensions. Conversely, the danger of losing it could add fuel to Moscow's desire to have a loyal government in Kyiv, no matter the price.