On Nov. 8, 1991, Boris Yeltsin declared a state of emergency in a small and distant region of the Russian republic — a mountain enclave called Chechnya.

Russia was still — technically — part of the Soviet Union, but already it was facing what would become in subsequent years its most severe challenge. Chechnya wanted to break free; Yeltsin thought that would pose a direct challenge to Russia’s viability.

The Muslim Chechens had been the last of the people of the Caucasus to be brought under Russian rule, in the late 1850s. At the end of World War II, Joseph Stalin had deported the Chechens en masse to Kazakhstan and Siberia, though they began to filter back in the mid-1950s. Then, immediately after the Soviet coup attempt in August 1991, a retired Soviet air force general named Dzhokar Dudayev had seized power in Chechnya from leaders who had backed the Moscow hardliners. Dudayev, in other words, had been on Yeltsin’s side in opposing the coup.

They didn’t stay on the same side for long. Dudayev wanted independence, and raised a militia. After imposing a state of emergency, Yeltsin sent troops, but Dudayev’s militia didn’t back down. The Supreme Soviet, Russia’s legislature, met. Though there was considerable umbrage directed at Dudayev, on Nov. 11 it declined to endorse Yeltsin’s moves. The next day he relented and began negotiating with the Chechen leader.

For the next three years, Chechnya was allowed to go its own way as long as it didn’t proclaim independence. It became a major hub of organized crime. Yeltsin, who had dismissed the Supreme Soviet with tanks in 1993, eventually felt forced to act. He tried to organize a coup against Dudayev, but it failed humiliatingly. In December 1994, he sent in troops and the first Chechen war began. Tens of thousands were killed, and the flaws of the Russian army became glaringly obvious.

After a truce, during which Dudayev was killed by a Russian missile that homed in on his satellite phone, a second war followed. With it came a surge of Islamist extremism in the Caucasus and Vladimir Putin’s rise to power in Moscow. Today, the Chechen capital, Grozny, has been rebuilt from ruins, and Chechnya is in the hands of a strongman named Ramzan Kadyrov, who in theory recognizes Russian sovereignty. No other ethnic group has followed the Chechens’ example, which had been Yeltsin’s biggest fear.