An assassin’s bullet among sectarian tensions was all it took to push the European powers into the catastrophic “war to end all wars” in 1914. By slaying an Austrian archduke, a Serbian gunman triggered a chain of events that savagely changed the face of Europe by bringing about World War I.

It is a moment in history worth remembering as we once more teeter on a historical precipice.
When it comes to the Syria conflict, recent developments may hurl us off the cliff. A series of escalations—including Israeli airstrikes on Damascus, Hezbollah’s decision to openly send thousands of fighters across the border, and the European Union lifting its arms embargo on the rebels—have dramatically increased the risk level. And given the signs that planned U.S.-Russian-endorsed talks in Geneva might not even get off the ground, there is evident cause for worry. Close observers now worry the Middle East is on the brink of a wider war—one that will have as profound repercussions for the region as World War I had for Europe.
“There is real danger of greater contagion,” says Dr. Jonathan Schanzer, a Middle East scholar at the Washington, D.C.–based think tank the Foundation for Defense of Democracies. A danger not alleviated by a Russian decision to supply President Bashar al-Assad with a new advanced air defense system.
But the complexities of the conflict, and the danger with U.S. intervention, was inadvertently demonstrated last week by Republican Sen. John McCain when he slipped into northern Syria to show his support for the Syrian rebels—and put pressure on the Obama administration to do more.
The senator was careful to align his trip with the moderates among the fractious rebel military commanders. But pictures emerged of McCain alongside members of the Asifat al Shamal brigade, a militia responsible for the kidnapping of a dozen Lebanese Shiite pilgrims last year.
A century ago, miscalculation was greatly to blame for thrusting Europe into a conflagration. A complex web of alliances made escape difficult and created, as the late British historian A.J.P. Taylor put it: a “rigid diplomatic framework, within which relatively small detonators could produce huge explosions.”
In the Middle East, the detonators are even more powerful than the retort of an assassin’s shot. And the weaponry in use (and continually arriving) is more sophisticated and deadly than what was deployed by the generals in the Great War.
This week, we saw the latest “detonator” in the form of an announcement by embattled Syrian President Bashar al-Assad who claimed Russia had started to deliver sophisticated S-300 air defense missiles to his country—weapons Israeli officials have warned would be considered a threat to Israeli security—and one they’re prepared to use force against. Beyond drawing Israel further into the conflict, such missiles could also make it harder for the Obama administration to impose a no-fly zone over the rebel enclaves of northern Syria.
How the conflict plays out in the coming weeks could be determined by whether Israel becomes more involved, says Christopher Preble, a foreign affairs scholar at the Cato Institute, a Washington, D.C.–based think tank. He says he still sees little appetite on Capitol Hill or within the Obama administration for U.S. military involvement—even for the imposition of a no-fly zone. “That would change, say, if Assad or Hezbollah attacked Israel,” he says. “Then all bets would be off.”
Meanwhile, the usually tentative European powers have joined the more bellicose part of the choir. This week, French Foreign Minister Laurent Fabius reacted angrily to reports in Le Monde that Assad forces had used chemical weapons in a suburb of Damascus. In a radio interview, Fabius warned of a “severe reaction,” if analysis of soil samples in a few weeks proved chemical weapons had been used. Asked what “severe” meant, Fabius responded: “It’s the final stage before a strike.”
The two-year-long Syrian conflict that has left at least 80,000 dead and displaced millions of Syrians has developed into a sort of proxy sectarian war, pitching Sunni Muslim Qatar and Saudi Arabia against the Shiites of Iran and Hezbollah while also inexorably drawing in Israel, the U.S., Russia, and the Europeans.
In Turkey and Jordan, nervous locals are now forming “citizen militias” in response to the conflict on the border. And in neighboring Lebanon, pro and anti-Assad forces are already fighting. For that country, the question is whether combat will reignite the bitter 15-year Lebanese civil war that left 120,000 Lebanese dead and a quarter of the population wounded.
In Syria near the Lebanese border, Schanzer notes, the struggle is now largely a “foreign fighter’s battle” with pro-Assad Shia Hezbollah militiamen battling Sunni rebel fighters from the al Qaeda affiliate Jabhat al-Nusra, many of whom have come from other Middle Eastern countries.
And Syrian rebel sources concede this. They admit that in the ferocious weeks-long struggle for control of the strategically important town of Qusair that lies between the Syrian capital of Damascus and the country’s third-largest city, Homs, al Nusra fighters are taking the lead. Likewise, they claim that there are few Syrian government forces now in the fight. “We are fighting Hezbollah,” one of the sources said via Skype.
Hezbollah aren’t the only ones battling on Assad’s side. Rebels claim Iran is deploying more fighters from the country’s al-Quds force, part of the Iranian government’s Revolutionary Guards.
And there is mounting evidence that Russia is keen to reassert itself in the Middle East and that the country has sent more military advisers into Damascus. That also raises the stakes, according to a Pentagon official, who spoke on condition his name wouldn’t be disclosed. As he put it: “What happens if we impose a no-fly zone in northern Syria and launch airstrikes on Syrian air force bases to make that happen and kill in the process some Russian military advisers?”
As he suggests, proxy wars can get out of hand. That is partly what happened in 1914 when the great European powers—Britain, France, Germany, Russia, and Austria—competed for geopolitical influence by backing rival nationalities and revolutionary groups in the Balkans. The consequence was the slayings of Archduke Franz Ferdinand and his wife, Sophie—and ultimately one of history’s deadliest conflicts.