May 9, or Victory Day, is a hugely important day for Russia's military. It marks the anniversary of the Soviet announcement in May 1945 that Nazi Germany had surrendered, and it is now celebrated with an enormous military parade in Moscow. The parade is an impressive show of strength: About 11,000 soldiers and more than 150 military vehicles gathered in Red Square on Friday.

In light of recent events, however, it's worth remembering how much that military relies on outside factors -- for example, a large number of factories and other resources in Ukraine's troubled southern and eastern regions.

Kateryna Choursina and James M. Gomez of Bloomberg Businessweek recently pointed out that more than 50 factories in Ukraine's southern and eastern regions provide significant amounts of important hardware for Russia's military, and that the Russian government's $15 billion agreement with former Ukrainian President Viktor Yanukovych (the agreement that eventually lead to his ousting) aimed to further intertwine the two country's defense industries.

The map below, compiled using information from the Royal United Services Institute, shows where some of the most important sites are for Russia, as well as the major sites of Ukraine's pro-Russian separatist movement. It shows not only how southeast Ukraine provides military hardware for Russia, but also controls oil and uranium, and even the food for the sailors in Sevastopol.

It's worth bearing this in mind when we consider the Russian military's buildup on the borders of Ukraine (whether or not they are gone). The troops don't just threaten Ukraine: They rely on it. too.