The BBC reports today that the 14-year-old ceasefire between Armenia and Azerbaijan was breached as fighting occurred between forces from both nations in the Nagorno-Karabakh region. The Azeri government is claiming that the Armenians intentionally started this incident to distract attention from extensive internal protests within Armenia over claims that last month's elections were rigged.
The conflict between Armenia and Azerbaijan is yet another one of those long-term ethnic conflicts that was contained behind the iron curtain for nearly a century, only to "spring to life" again in the late 80s and early 90s. Around the time of the inception of the Soviet Union, the NK territory had a majority Armenian population. Based on this, the Soviets converted it into an autonomous territory within the nation of Azerbaijan. As the Azeri population increased over time, the ethnic Armenians within the NK territory pushed for unification with Armenia. The formal attempt to do so in 1988 sparked reciprocal massacres of Armenians and Azeris, and prompted the Soviets to give the government of Azerbaijan a freer hand in how it policed the territory.
By 1989, Azerbaijan was actively blockading trade between Armenia and the other Soviet Republics (I bet you had no idea this was going in at the time). Gorbachev's proposal for increased autonomy within the NK territory was met by ethnic violence against Armenians in Azerbaijan, which in turn prompted the Soviets to send an armed presence, killing a number of Azeris.
In 1991, on a day now cited as the independence day of the Nagorno Karabakh Republic, an Armenian referendum within the territory declared it an independent state. This amounted to an immediate secession of about one-fifth of Azerbaijan and the displacement of one million Azeris. Local Armenian forces attacked Azeri forces, pushing them out of the new state and capturing territory to bridge them with Armenia proper. Russia mediated a ceasefire in 1994 -- the same ceasefire that was breached in today's military action.
All told, things seem to have worked out tremendously poorly for Azerbaijan. Russia came in firmly on the side of Armenia, to the tune of a billion dollars in arms during and after the last years of the war, and a friendship agreement between the two nations that included promising fuel supplies from Gazprom to make up for fuel lost due to the Azerbaijani blockade. In contrast, the Azeris have been punished by, among others, the United States for imposing that blockade. That seems, in a word, unfair.
You can read more from the NK Armenian point of view at the website of the NK Republic, or at the website of their DC office. You can read a general summary of the entire situation here at GlobalSecurity.org. You can read more about the Azerbaijani point of view at their embassy web page, including this specific page on the NK conflict, and a recent press release on a massacre of Azeris by Armenian troops in 1992 (that last one is a PDF).
BBC article