You cannot understand the Chechens without understanding the mountains. The mountains created them as surely as the cold Atlantic created the Britons, or the frontier created the Americans.
The mountains were, for millennia, effectively impassable. Armies could go around the eastern end, through Azerbaijan and Dagestan on the shores of the Caspian Sea. Or they could pick their way along the Black Sea Coast, providing their horses and infantry did not mind getting their feet wet.
Between the two seas, however, was the rampart of the Caucasus, the highest range in Europe, which could only be crossed on foot and even then often only in summer. South of the mountains was the majesty of the ancient world: Byzantium, Persia, Alexander the Great, Assyrians, Medes and the rest of them.
There were empires south of the mountains, but north of the mountains the peoples had no need to unite to resist invaders. Villages ruled themselves, acknowledged no overlord, robbed each other and traded, safely protected from conquest by the peaks at their backs.
Or, they were -- until the Russians came.
Expanding southwards, first in a few exploratory missions under Peter the Great and then in force under Catherine the Great, the Russians fought all before them: the Nogais of the steppes, the last free descendants of Genghis Khan; the Tatars of Crimea; and finally the Chechens, and the other peoples of the Caucasus.
The clash between the armies of the autocratic, centralized, militaristic Russian state with the horsemen of the anarchic, freebooting Caucasus, who were too disorganized to trouble anyone more than a day or two's ride away, was the biggest culture clash in European history. The Russians won the first engagements, but the Chechens' response was not long in coming.
"In the village of Aldy a prophet has appeared and started to preach. He has submitted superstitious and ignorant people to his will by claiming to have had a revelation," wrote a Russian major general in 1785.
The Russians marched on Aldy, and destroyed it, but the prophet -- a man called Ushurma but now known as Sheikh Mansur -- was lying in wait. Half the Russian force of 3,000 died in an ambush on their way home, and Mansur became a hero for the Muslims of Chechnya and neighbouring Dagestan.
Mansur did not last. After a few victories, he fled, was captured and died of tuberculosis in a fortress near Saint Petersburg. But he was the first manifestation of the Russians' great enemy in the Caucasus -- the welding of Islam with nationalism into a single potent combination.
Over most of the next century, religious leaders led the highlanders of Chechnya and Dagestan in opposition to the Russians. Their resistance was heroic but it was, ultimately, doomed. They were, after all, fighting against Russia, the power that defeated Napoleon. As Imam Shamil, the highlanders' last leader, is said to have remarked when he was being taken to see the tsar after his surrender in 1859: "If I had known Russia was so big, I would never have fought against it."
Shamil, a Dagestani, was brutally frank about the Chechens, who would fight for him but refused to obey him in any other way, as they have refused to obey rulers, either foreign or their own, to the present day.
"There is nothing worse than this trash in the whole world. The Russians should say thank you to me that I corrected them a little. Without this, you would have only one way to deal with them: shoot them to the last man, as is done with harmful animals," Shamil told his Russian guard, according to the guard's diaries.
The Russians took him at his word. Although, the Chechens lived on in their homeland, they lived as a defeated nation, their best land given to Cossacks and their culture never given a chance to develop. When the tsarist government fell, it had done almost nothing to transform the anarchic highlanders into model Russian peasants and, after 1917, the new communists promised to help them find enlightenment in the modern state they would create.
"These people were doomed to incredible suffering and extinction," one official, the commissar for nationalities, told the Party Congress in 1921. He knew of what he spoke, because he was from the Caucasus himself. His name was Josef Djugashvili, though he is better known today as Stalin.
Hidden within his promise was a mistaken assumption, however, which was that the Chechens actually wanted to live as full Soviet citizens, which they didn't. "Bandits" continued to haunt the mountains. Some 35,000 Chechens were purged in 1931, and another 14,000 six years later. Still, the Chechens would not submit and, by 1944, Stalin had come to the same conclusion as Imam Shamil: The Chechens should be wiped out.
On Feb. 23 -- a holiday in the Soviet Union, on which citizens honoured the soldiers of the Red Army -- troops moved in, rounded the nation up, packed it onto trains and shipped it to Central Asia. Thirty-five percent of the deportees died, either in the packed cattle cars or on the freezing steppes when they arrived in the depths of the cold Kazakhstan winter.
This is the defining moment in Chechens' modern history, when they were wrenched away from their mountains and dumped like rubbish in an unfriendly land with a flat horizon. Even the Russian government has recognized this was a genocide, and yet few Russians today appreciate the trauma it caused. Everyone lost someone and, when they were allowed home beginning in 1959, many of those bodies came home to Chechnya with them, to be buried in the mountains, not in the foreign steppes.
They were kept together by their faith, by their Sufi Islam with its closed brotherhoods and secret rituals. The generation that grew up in Kazakhstan nursed a seed of grievance. That seed grew in the fertile soil of Mikhail Gorbachev's perestroika, and flowered into a declaration of independence in the dying days of the Soviet Union.
Of Boris Yeltsin's many disastrous decisions, few were as terrible as the idea that a quick war against the rebellious Chechens would help boost the new Russian president's flagging poll numbers toward the end of 1994.
He sent in the tanks, thus uniting a nation that was sinking into in-fighting. He ordered the tanks out again two years later. Moscow's mighty army was defeated in the streets of Grozny by Chechen irregulars, and the superpower's impotence was laid bare for all to see.
But these were the Chechens, ungovernable even by their own, even by Aslan Maskhadov, the man who had led them to their unlikely victory over a country with more people in uniform than there are Chechens.
Without an external enemy to unite them and, no doubt, aided by trained provocateurs sent by Moscow, they fell into squabbling among Islamists, mafia gangs, secular nationalists and ordinary Chechens who just wanted to get on with things.
In 1999, the Chechens invaded Dagestan, supposedly to aid allies there, and a new Russian leader decided Moscow had had enough. Prime Minister Vladimir Putin was making none of Yeltsin's mistakes, however. He had no intention of fighting among the tower blocks of Grozny. His artillery flattened the Chechens' capital block by block, driving his opponents into the open, where they died on mines or explosions or in extrajudicial executions.
International sympathy drained away over the succeeding years as Chechen insurgents resorted to the most terrible of atrocities in attempts to force Russia to the negotiating table: seizing a theatre in Moscow, a school in Beslan, and blowing up trains, buses and planes. None of it worked. Moscow's grip tightened and thousands of Chechens fled forever, forming diaspora communities in Western Europe, the Gulf and the Middle East.
And that is how the Tsarnaev brothers ended up -- via Dagestan and Kyrgyzstan -- in Boston, ungovernable men of the mountains, warlike, disorientated, come to fight a pointless and unjustified fight thousands of miles from the mountains they once called home.
Oliver Bullough is Caucasus editor of the Institute for War and Peace Reporting and author of Let Our Fame Be Great, Journeys Among the Defiant Peoples of the Caucasus.