RED ARMY HEIRS
Both militaries are the successors of the Soviet army and have inherited its arsenals, structure and tactics. Ukraine surrendered its share of Soviet nuclear arsenals to Russia in the early 1990s.
The Russian military is much bigger, at 1 million men, compared to Ukraine's 180,000. The Ukrainian military has an estimated 200 combat aircraft and about 1,100 tanks, while Russia reportedly has about 1,400 combat aircraft and several thousand tanks.
Russia and Ukraine divided the Soviet Black Sea Fleet after the 1991 Soviet collapse. However, Ukraine has struggled to maintain its share of the fleet and has just a few combat-ready ships, far outnumbered by the Russian navy, which has a lease of the Crimean port of Sevastopol until 2042.
The Russian military has undergone a major modernization in recent years, receiving large supplies of new weapons and conducting massive exercises. Cash-strapped Ukraine couldn't afford such a buildup and its forces have slowly degraded.
In addition to the funding shortage, the Ukrainian military's readiness was hurt by last year's decision by President Viktor Yanukovych to end conscription and turn the military into a volunteer force. The last wave of conscripts is half way through its one-year term, and their morale could be low. The new Ukrainian government has tried to call up some reservists, but it's unclear whether that will work.
The Russian military has largely recovered from its post-Soviet meltdown, and it recently has run a series of war games unseen since the Cold War times. An exercise involving 150,000 troops, hundreds of tanks and dozens of combat planes has been launched across western Russia just as Russian forces overtook Crimea. President Vladimir Putin attended the maneuvers Monday at a shooting range near St. Petersburg.
Ukraine's loyalties have been sharply divided between the Russian-speaking east and south, where people favor close ties with Moscow, and the west, where residents want to integrate more closely with the European Union.
Ukraine's armed forces reflect that divide. Units stationed in Russian-speaking regions are mostly manned by local residents who don't necessarily support the new government in Kiev. That raises doubts about their loyalties in case of a military conflict with Russia.
The Ukrainian military's reluctance to confront the Russians became obvious in Crimea, where a newly-named Ukrainian navy chief went over to the pro-Russian local government, a day after his appointment. Regional officials say that thousands of Ukrainian servicemen have done the same, but that claim can't be independently confirmed.
TENSE STANDOFF IN CRIMEA
Forces of Russia's Black Sea Fleet based in Crimea and additional Russian troops sent to the peninsula have seized or blocked Ukrainian air bases, air defense missile batteries and other military facilities, and garrisons throughout the region. Ukraine's military acknowledged that "practically all" of its military facilities in Crimea have been surrounded or taken over.
A ferry crossing linking Crimea with Russia has been overtaken by Russian forces, which would allow a quick military buildup in Crimea, if Russia chooses to do so. A narrow strip of land linking the peninsula with mainland Ukraine also has been sealed by armed people.
The Ukrainian military said Russia has recently brought four navy ships from other seas to the Crimean port of Sevastopol.
The Russians have demanded that Ukrainian soldiers in Crimea lay down their weapons. Some have agreed and left or joined pro-Russia forces. But others have refused and barricaded themselves at their bases.