"On this festive day we show our resolute protest against the plans of NATO countries aimed at expanding the military-political bloc farther east," said one of the organizers, Russian Bloc lawmaker in the Crimean parliament Oleg Slyusarenko.
Police estimated that the rally, which took place outside the parliament building in the center of Simferopol, was attended by around 400 people, including activists from the Ukrainian opposition Party of Regions, some holding banners reading "Ukraine's future - union with Russia."
"We are certain that NATO soldiers will never be in Crimea, and that Sevastopol will forever remain the main base of Russia's Black Sea Fleet," said the deputy speaker of Crimea's parliament, Sergei Tsekov.
Russia's Black Sea Fleet uses a range of naval facilities in Ukraine's Crimea, including the main base in Sevastopol, as part of a 1997 agreement, under which Ukraine agreed to lease the bases to Russia until 2017. Ukrainian President Viktor Yushchenko said last year that Ukraine would not extend the lease.
In Kiev, Prime Minister Yulia Tymoshenko laid flowers at the tomb of the Unknown Soldier in honor of Defender of the Fatherland Day, while Yushchenko, who does not recognize the holiday, spent the day - his 55th birthday - at his residence in western Ukraine.
With the breakup of the Soviet Union, Ukraine ceased to recognize many Soviet holidays, and Armed Forces Day was introduced on December 6. However, in 2004 then-President Leonid Kuchma reintroduced February 23 as Defender of the Fatherland Day.