Yugoslavia disintegrated in a series of bloody wars in the early 1990s.
Vicious fighting erupted between Croatia and its Serb minority, strongly backed by Belgrade, after Zagreb declared its independence in June 1991.
Four years of bloodshed ended with 20,000 dead and with Croatia taking back territories held by Serb secessionists.
Neighbouring Bosnia's proclamation of independence in 1992 after a vote boycotted by the Serbs unleashed a three-and-a-half-year war that for a period became a three-way fight when Croats turned on their Bosnian Muslim allies. It left nearly 100,000 dead, two-thirds on the Bosniak side.
Nagorny Karabakh (1991-1994 and 2020)
Ex-Soviet states Azerbaijan and Armenia have feuded over the Nagorny Karabakh region since Armenian separatists seized the territory in a war that claimed some 30,000 lives in the early 1990s.
War broke out again in late 2020, with a rearmed Azerbaijan winning a crushing victory over Armenia, forcing it to cede large parts of the mostly Christian and ethnically Armenian region. At least 6,500 died.
North Ossetia (1992)
Russia's North Ossetia and Ingushetia fought a brief but deadly conflict in the 1990s over the Prigorodny Raion, a district which became part of North Ossetia under the Soviet Union but that has been disputed by the Ingush ever since.
The 1992 conflict claimed hundreds of lives and created tens of thousands of Ingush refugees after Moscow intervened to help the Ossetians.
Transnistria, or Transdniestr, made its bid for secession in 1990 as the Soviet Union crumbled, fearing domination by the Romanian-speaking population that makes up the majority in the rest of Moldova.
Chisinau tried to recover Transnistria without success. Skirmishes turned into a short war in 1992, in which several hundred people died.
Russia has kept soldiers in Transnistria since despite a commitment in 1999 to remove them.
The semi-independent statelet is not recognised by any country, including Russia.
Chechnya (1994-1996, 1999-2009)
Chechnya, a majority Muslim republic in the Caucasus, was twice the scene of deadly wars between the Russian army and separatists, leaving tens of thousands of dead.
In late 1994 Moscow sent in troops to bring separatist Chechnya to heel. Meeting fierce resistance, the Russians withdrew in 1996.
But then prime minister Vladimir Putin sent troops back in again in October 1999 for what he called an "anti-terrorist operation." Russia pacified the region, retaking the capital Grozny after a siege, with the United Nations calling it the most destroyed city on Earth.
In March 1998 Belgrade launched its first offensive against ethnic Albanian guerrillas in Kosovo, then a southern Serbian province with an overwhelming ethnic Albanian majority.
The offensive triggered a NATO intervention in March 1999 that forced Serb troops out by June 10.
Some 13,000 people died, overwhelmingly ethnic Albanians.
In August 2008 the Georgian army tried to retake breakaway South Ossetia, of which it had lost control following the fall of the Soviet Union and a war in the early 1990s.
Russia immediately riposted, sending its troops into Georgian territory and dealing the pro-Western ex-Soviet state a crushing defeat in five days.
The Kremlin then recognised the independence of South Ossetia and Abkhazia, another separatist Georgian province.
Ukraine (2014 and 2022)
Tensions between Moscow and Kyiv gradually deteriorate in the three decades following Ukrainian independence in 1991.
In 2014, after a pro-European Union revolution forced out the Kremlin-backed leader Viktor Yanukovych, Russia retaliated by annexing the Crimea peninsula.
Moscow also backed a revolt by the separatist regions of Donetsk and Lugansk in eastern Ukraine along the border with Russia. They declared independence, unleashing an intense armed conflict with Kyiv, in which 14,000 people died.
On Thursday, Russia invaded its smaller neighbour.