In early August 2008, after Georgian President Mikheil Saakashvili sent troops into the rebellious province of South Ossetia, Russia came to its defense, beginning a five-day-long conflict that ended with Russian troops within striking distance of Tbilisi, the Georgian capital.

Moscow’s aggressive reaction to its long-simmering tensions with Georgia announced Russia’s reemergence as a military power, and paved the way for its controversial dealings with another former Soviet republic, Ukraine, beginning in 2014.

The roots of the Russia-Georgia conflict go back to the early 1990s, when both Russia and Georgia were newly independent nations after the dissolution of the USSR. Civil war erupted within Georgia, located to the south of Russia on the eastern shore of the Black Sea, when two provinces—South Ossetia in eastern Georgia, and Abkhazia, on the northwestern coast—sought to declare their own independence.

“One can track [the 2008 conflict] back, really from the very beginning of the independence of Georgia, when Abkhazia in particular split away, and the Russians backed Abkhazia,” says Mark Galeotti, senior non-resident fellow at the Institute of International Relations Prague and an expert on modern Russian history and security affairs.

A ceasefire in 1994 ended the worst fighting, but tensions continued to simmer in the two breakaway provinces, which remained technically part of Georgia. Home to different ethnic groups, the Ossetians and the Abkhazians, they had been autonomous earlier in the 20th century, after the Russian Revolution, and they wanted their autonomy back.

Beginning in the late 1990s, the European Union and the North Atlantic Treaty Organization (NATO) expanded their influence in Eastern and Central Europe, formerly a Soviet stronghold. Russia and its new president, Vladimir Putin (first elected in 2000), bitterly resented the loss of this buffer zone between Moscow and the West.

For its part, Georgia was moving further West, even joining the U.S.-led coalition fighting in the Iraq War in 2003. This process intensified after the election of pro-Western President Mikheil Saakashvili in 2004.

“Georgia was clearly embarked on a process of trying to break out of Russia’s sphere of influence,” Galeotti says. “And as far as Russia was concerned, this was an absolute priority. It had to maintain its sphere of influence, and if it let Georgia go, then who could be next?”

Sakaashvili also attempted to crack down on separatism within Georgia, which brought the long-running conflict in South Ossetia into the forefront again. Georgia’s always-tense relationship with its northern neighbor worsened in late 2006, when Sakaashvili’s government accused Putin, who was Russia’s prime minister at the time, of supporting the separatist cause. After Georgia arrested four Russian military officers for suspected espionage, Russia responded by closing Georgian businesses and deporting Georgian citizens.

With Georgia on the verge of joining NATO, but not yet subject to the organization’s collective defense agreement, Russia saw an opportunity to rein in its neighbor and demonstrate its military strength in the region. As Galeotti puts it: “The Russians built up their plans, built up their forces, and they ensured that their local proxies in South Ossetia needled Georgians enough, knowing that Sakaashvili….would rise to the bait.”

On August 8, 2008, after months of back-and-forth accusations and provocations between the two sides, and a series of clashes between South Ossetian militia and Georgian military troops, Sakaashvili ordered his troops to capture the South Ossetian capital of Tskhinvali. Russia swiftly responded by moving its troops to the border and conducting air strikes on Georgian positions in South Ossetia as well as Abkhazia.

With the United States, Great Britain and NATO calling for a ceasefire, the conflict continued for five days, as Russia quickly took control of Tskhinvali and rolled its tanks and troops through Ossetia into Georgia, stopping only about 30 miles from Tbilisi, the Georgian capital.

Beyond diplomatic efforts and humanitarian aid, the international community did little to stop the conflict. “No one was willing to go to war for Georgia,” Galeotti points out. “This was a time in which no one really wanted to provoke Russia. [Dmitry] Medvedev was president, and particularly American policy was to essentially hope that this could be leveraged into something more positive. So…to a large extent, Georgia was left on its own.”

After Russia called a halt to its advance into Georgia, a cease-fire on August 12 ended the Russia-Georgia War. According to an official EU fact-finding report in 2009, nearly 850 people were killed during the five-day conflict, while some 35,000 Georgians were left homeless. That same fact-finding report concluded that though Georgia had initiated the war, Russia had provoked its neighbor over a long period and overreacted to that initial artillery attack.

Though Russia formally recognized South Ossetia and Abkhazia as independent states after the war, few other countries have joined them in doing so. Meanwhile, Georgia turned further away from Russian influence in the aftermath of the conflict, and signed an association agreement with the EU in 2014.

Perhaps the most lasting consequence of the Russia-Georgia War can be seen in what happened six years later, in Ukraine. With Putin back as president (and Medvedev as prime minister), Kremlin-backed forces seized control of the Crimean peninsula and parts of the Donbass region in 2014. Russia had undertaken a “much more serious military reform program,” in the wake of the Georgia war, Galeotti explains, “which led to the far more competent forces that we saw in the annexation of Crimea.”

Moreover, by not coming to Georgia’s defense in the lopsided 2008 conflict, the international community had proved to the Russians that it was “essentially lacking in the will to back up its fine words,” Galeotti says. “In hindsight, one wonders, would Crimea and the Donbass wars have happened if the West had been more robust in its response to Georgia?”