SEVENTY-TWO Turkish fighter jets cut through the skies above north-west Syria on January 20th, dropping bombs on the Kurdish enclave of Afrin, while thousands of Turkish troops massed at the border. They were joined by busloads of Syrian rebels, Turkey’s proxies in the fight against Bashar al-Assad’s blood-soaked regime in Damascus. So it was that Turkey opened a new front in the Syrian war, and in its unending conflict with Kurdish insurgents, with reverberations rippling to Washington, Moscow and Istanbul.

The offensive pits NATO’s second-biggest army against a Kurdish militia called the People’s Protection Units (YPG), which Turkey says is a branch of its domestic foe, the Kurdistan Workers’ Party (PKK). The separatist PKK has fought an on-off insurgency against Turkish security forces for over three decades. But the YPG is best known for fighting Islamic State (IS) in Syria. American support, in the form of weapons and air strikes, helped the Kurds repel the jihadists and, to Turkey’s dismay, take control of vast stretches of land in the north (see article). When America said it would create a 30,000-strong “border-security force” in north-east Syria consisting largely of YPG fighters, Recep Tayyip Erdogan, Turkey’s president, vowed to “strangle it before it is born”.

The incursion, which is inexplicably called Operation Olive Branch, appears to enjoy wide support across Turkey. The media have whipped themselves into a nationalist frenzy almost as big as the one that followed an abortive coup in 2016. Of the four main parties in parliament, only one, a pro-Kurdish outfit whose leaders have been locked up for over a year, refused to support the offensive. Mr Erdogan argues that an emboldened YPG plans to use the Syrian borderlands in the same way as the PKK has used the mountains of northern Iraq: as a launching pad for attacks against Turkey. Most Turks seem to agree with him.

The stubborn sultan

Mr Erdogan has ways of dealing with those who do not. Having caught wind of possible protests, he pledged to “crush anyone who opposes our national struggle” and warned that police would be “breathing down the necks” of those who took to the streets. Dozens of people, including at least five journalists, have been detained for social-media posts criticising the offensive. In Northern Cyprus crowds of Turkish nationalists attacked the office of a local newspaper that likened Operation Olive Branch to Turkey’s invasion of the island in 1974—ie, an illegal occupation.

The precise aims (and limits) of the operation are unclear. Turkey’s chief of the general staff, Hulusi Akar, has said he will push forward “until we eliminate every terrorist”. Other officials liken the offensive to one in 2016 that saw Turkey wrest from IS a 100km stretch of Syrian territory west of the Euphrates river. The jihadists hardly put up a fight and local Arabs and Turkoman welcomed the Turks as liberators. (Turkish troops and Syrian rebels are still in control of the area.) “We’re hoping to repeat this example in Afrin,” says Bekir Bozdag, Turkey’s deputy prime minister.

But the Turks will face a much tougher fight in Afrin. Around 10,000 battle-hardened YPG fighters are in the area. Local Kurds, who are most of the enclave’s 600,000 or so residents, seem uniformly hostile to the Turks and their Syrian allies. The YPG has closed roads out of the city, while the Assad regime turns back those who manage to leave. According to the Syrian Observatory for Human Rights, a Britain-based monitoring group, at least 28 civilians, 42 Kurdish fighters and 48 Syrian rebels were killed in the first five days of the operation. Officials in Ankara confirmed the deaths of three Turkish soldiers and claimed to have killed 268 militants. Rockets believed to have been fired by the YPG killed three people in the Turkish towns of Kilis and Reyhanli.

America is caught in the middle—and sending out mixed messages. The Pentagon hopes to continue using the Kurds as a bulwark against Islamist militancy in Syria. The White House, though, has disavowed plans to create a new Kurdish-led force and downplayed America’s relationship with the Kurds. In general, American officials have been loth to criticise Turkey, but in a phone call with Mr Erdogan on January 25th, President Donald Trump expressed concern about the violence in Afrin. So says the White House, at least. A Turkish source said no such concerns were shared.

While America loses leverage in Syria, Russia is filling the vacuum. It has mended its relationship with Turkey, which reached a low point in 2015, when the Turks shot down a Russian fighter jet over Syria. Happy to stoke tension between America and its allies, Russia almost certainly gave the operation in Afrin a green light. It may be that in return Turkey looks the other way as Russian and Syrian forces pound rebels in Idlib, who are ostensibly allied with Turkey against the Assad regime. But some think the Russians will eventually turn on Turkey and cut a deal with the Kurds that hands Mr Assad control of Afrin.

A more immediate concern is whether the Turks plan to push into other YPG strongholds. America has some 2,000 troops stationed in Syria, many in the Kurdish-held north-east. If Turkish troops start shooting at YPG fighters in those areas, American soldiers could end up in the crossfire. The result could be a direct clash between NATO allies.