And now, Ukraine's beleaguered interim government is warning that it might call a halt to all arms supplies to Russia: "Manufacturing products for Russia that will later be aimed against us would be complete insanity," Vitaliy Yarema, Kiev's first deputy prime minister, said.
Such a move, experts say, could cause serious damage to Russia's military capacity, by greatly increasing the costs of the sweeping modernization ordered by the Kremlin after Russia's 2008 war with Georgia exposed serious shortcomings in the country's military preparedness. But in the longer term, experts add, the economic pain is likely to be felt more deeply in Ukraine, for whom Russia is the irreplaceable market for about 90 percent of its military exports.
Russo-Ukrainian military industry
The Kremlin is taking the prospect of a cutoff very seriously. At a government meeting Wednesday, President Vladimir Putin ordered emergency measures to work around any sudden cutoff of military components from Ukraine and promised to find funds to pay for it. "We need to look ahead and work out which Russian companies, in what time frame, and at what cost could produce these goods," Mr. Putin told his ministers.
Russian Industry Minister Denis Manturov told Putin that the value of outstanding orders from Ukraine in the "civilian and defense" sectors is more than $15 billion. Analysts say a major part of that would be military parts and equipment.
"This is a really unpleasant moment for Russia," because military cooperation with Ukraine was vital, says Viktor Litovkin, a military expert with the official ITAR-Tass news agency.
Though military integration between Russia and Ukraine is well down from its Soviet-era peak, Ukraine still makes a surprising number of essential parts that go into modern Russian weaponry.
According to a 2009 survey by Kiev's Razumkov Center, Ukrainian factories produce the engines that power most Russian combat helicopters; about half of the air-to-air missiles deployed on Russian fighter planes; and a range of engines used by Russian aircraft and naval vessels. The state-owned Antonov works in Kiev makes a famous range of transport aircraft, including the modern AN-70. The Russian Air Force was to receive 60 of the sleek new short-takeoff-and-landing aircraft, which now it may have to do without.
Valentin Badrak, director of the Center of Army Studies in Kiev, says that even Russia's new Ilyushin Il-476 transport aircraft, which is built in the central Russian city of Ulyanovsk, cannot be produced without Ukrainian spare parts. He says Russia will be hurt by a cutoff of cooperation in "several spheres.... In Ukraine we have about two dozen companies that had projects with Russia important to Russia's security and defense."
The mainstay of Russia's strategic missile forces is the SS-18 Satan multiple-warhead intercontinental ballistic missile, all of which were produced in Soviet times at the giant Yuzhmash works in Dnipropetrovsk, and which still rely on Ukrainian expertise to keep in working order. However, the Razumkov report notes that Russia's next generation of strategic missiles, including the mobile Topol-M, are entirely produced in Russia.
"We have our own specialists who can service the Satan missiles," says Mr. Litovkin. "The problem is mostly a legal one," because the Ukrainians have the propriety rights to do that work, he adds.
Selling Russian secrets?
The Kremlin may also be worried that a Ukraine freed from its contractual obligations to Moscow might go out and sell Russian military secrets to other countries.
Russia's foreign ministry posted an unusual note earlier this week warning that Ukrainian representatives of Yuzhmash, which built the SS-18, were meeting with "representatives of some countries, regarding the sale of a production technology for heavy-class intercontinental ballistic missiles."
It added "we trust that despite the complicated foreign policy situation in Ukraine and the lack of legitimate supreme authorities, the current leaders of the country will be responsible, will fully comply with their obligation" to fulfill legal requirements and international rules against the proliferation of missile technologies.
Some Russian bloggers suggested that Ukraine was trying to sell Russian heavy missile technology to Turkey, a NATO country.
Costs for Ukraine
Experts say that Russia's dependence on Ukraine is a Soviet-era habit that, once broken, will prove to be a boost to Russia's own military-industrial development.
"I think we will survive this stroke of misfortune," says Litovkin. "Russian industry can compensate for the losses, but it will require investment and may take some time."
For Ukraine, on the other hand, severing military manufacturing ties with Russia could be devastating in the long run. Ukraine makes few complete weapons systems – other than T-84 tanks, some Soviet-era air defense missiles, and Antonov planes – and would struggle to find alternative markets for its mainstay production of Russian military hardware components.
"For the Ukrainian military-industrial complex, it will be a disaster," leading to plant closures and tens of thousands of unemployed workers, predicts Igor Korotchenko, director of the independent Center for Analysis of World Arms Trade in Moscow.
"As for Russia, the situation is bad," he adds, "but we'll survive."