Chechnya is one of 21 republics among the 89 regions that make up the Russian Federation.
It is located on the northern slopes of Europe's tallest mountain range, the Caucasus, not far from the Caspian Sea.
The Chechens are a Muslim people, who fought hard to avoid being incorporated into the Russian empire, but finally lost the battle in the 19th Century.
When the Soviet Union began to collapse in 1991, Chechnya tried to break away from Russia by declaring independence.
Moscow first sent tanks to Chechnya, to topple its separatist leaders and curb organised crime, at the end of 1994.
The Russian forces were routed in their first battle and were ultimately driven out of Chechnya in August 1996.
They were sent back in 1999 by Vladimir Putin - then prime minister, later president - after 300 people died in a chain of bombings blamed on Chechens.
Chechen rebels had also provoked Moscow by inciting an Islamist uprising in the neighbouring republic of Dagestan.
Russia's huge military presence in Chechnya has driven rebels underground and into mountain hideaways.
But they continue guerrilla warfare against Russian troops and Chechnya's pro-Moscow government, while staging sporadic attacks around Russia.
With time, their suicide bombings and hostage-taking raids have become increasingly bloody and desperate.
The power of the most radical rebel leaders has grown, undermining their more moderate chief, Aslan Maskhadov.
Moscow has tried to stabilise Chechnya by electing new leaders and getting voters to back a constitution that locks it into the Russian Federation.
Russian leaders refuse to hold talks with the Chechen rebels, describing them as terrorists backed by al-Qaeda.
But the legitimacy of the new Chechen leaders has been questioned by election monitors who say votes were rigged.
The first man Moscow backed to become Chechnya's president, Akhmad Kadyrov, was assassinated in May 2004.
The Chechen wars began as a struggle by Russia to re-assert its authority over a rebellious region whose leaders were determined to hang on to independence.
But religion has come to play an increasing role.
The rebels rely on funds from Arab donors and have given key jobs to Arab commanders. Muslim volunteers from many countries have fought on their side.
Russia and the US say the rebels have links to Islamic terrorists, such as al-Qaeda, but not all experts agree.
The war in Chechnya has been marked by brutality and abuses of human rights on both sides.
Chechen rebels have killed and beheaded civilians, bombed aircraft and trains and carried out hostage-taking raids on hospitals, a theatre and a school.
Russian forces have razed villages and large parts of the Chechen capital, Grozny, killing thousands of people.
Human rights groups have accused Russian troops of torture, rape, extortion and extrajudicial executions.