BEIRUT (AP) -- As Syrian President Bashar Assad and his allies push toward final victory and the fight against the Islamic State group draws to an end, new fronts have opened up, threatening an even broader confrontation among regional and world powers.
While large areas of the country have stabilized, giving the impression of a war that is winding down, violence has exploded in other areas with renewed ferocity, killing and injuring hundreds of people in a new and unpredictable spiral of bloodshed. The United States, Israel and Turkey all have deepened their involvement, seeking to protect their interests in the new Syria order.
The recent chaos has been exceptional: within a week, al-Qaida-affiliated rebels shot down a Russian jet, Kurdish fighters downed a Turkish helicopter, Israel downed an Iranian drone and the Syrian army shot down an Israeli F-16.
Meanwhile, a joint Russian and Syrian air campaign killed hundreds of civilians in the rebel-held enclaves of Eastern Ghouta and in the northern province of Idlib, amid accusations that the Syrian government is once again using toxic agents such as chlorine against its opponents.
In the east, the U.S. military launched rare airstrikes on pro-government fighters following a coordinated assault on U.S.-backed forces accompanied by U.S. advisers. That has increased fears that American troops meant to fight Islamic State militants increasingly are being dragged into the war.
Over the weekend, a battle erupted along Syria's border with Israel, which shot down an Iranian drone that infiltrated its airspace before one of its own fighter jets was downed by Syrian air defense missiles. It was the most serious flare-up between the neighbors since fighting began in Syria in 2011.
All this happened while Turkey's air and ground operation against Kurdish fighters in northwestern Syria rages on with no end in sight.
"The specter of the world's worst civil war in decades is becoming demonstrably worse by the week - and even more complicated by the actions of outside forces - creating a perfect storm of chaos and suffering in Syria," the Soufan Center said in an analysis of the situation.
Here is a look at some of the new and old fronts in Syria's war:
TURKEY'S WAR ON KURDS
Turkey opened a new front in Syria's nearly 7-year-old war on Jan. 20, launching an offensive against the U.S.-backed Syrian Kurdish militia in the northwestern enclave of Afrin. It is the latest effort by Turkey to limit Kurdish expansion along its border with Syria and aims to drive out the militia known as the People's Protection Units, or YPG, which Turkey considers to be a "terrorist" organization.
The Turkish campaign has strained relations between NATO allies Ankara and Washington, which has partnered with the Syrian Kurds in the fight against the Islamic State group. Turkey's president is threatening to expand the offensive east, toward the town of Manbij, where U.S. troops maintain bases, while U.S. officials accuse Turkey of hampering the fight against IS with its Afrin operation.
Residents speak of a rapidly worsening humanitarian situation, adding that medical supplies are running low. The Syrian Observatory for Human Rights says around 80 civilians have been killed so far, along with more than 160 Kurdish fighters. Turkey says it has lost 31 soldiers in the slow-moving offensive.
ASSAD'S WAR ON REBELS
The Syrian government and its ally, Russia, have in the past two weeks dramatically escalated attacks on two of the largest and most important remaining opposition-held areas, in Idlib province in northwestern Syria and on Eastern Ghouta, a besieged area near the capital of Damascus.
The sprawling region, where rebels launch rockets on Damascus, has been a particular thorn in the government's side for years, and Assad appears determined to recapture it at all costs.
The recent violence has left hundreds dead and wounded amid relentless airstrikes that have transformed the besieged area into a death trap. In Idlib, the bombardment has hit hospitals and created yet another wave of displaced civilians.
U.N. High Commissioner for Human Rights Zeid Ra'ad Al Hussein called on Saturday for urgent international action, saying the past week in Syria "has been one of the bloodiest periods of the entire conflict."
The commissioner said the "no-holds-barred nature" of the assault included attacks on nine medical facilities and the death of 277 civilians between Feb. 4 and Feb. 9 in both Idlib and Eastern Ghouta. There were also reports of the government using toxic agents in residential areas.
In Eastern Ghouta, nearly 400,000 residents are trapped by the violence and a tightening government siege. At least 2 million people live In Idlib, the largest area controlled by the opposition.
ISRAEL'S WAR ON IRAN
The downing of an Israeli fighter jet this weekend by Syrian air defenses suggest yet another frontier in the conflict is opening up, risking a wider and possibly regional conflagration.
Israel, which has struck targets inside Syria more than a 100 times in the course of Syria's war, with raids often launched from neighboring Lebanon's airspace, has been warning of an Iranian buildup in Syria for months, vowing to prevent Tehran from building bases near its border. On Saturday, Israel's military said it shot down an Iranian drone that took off from a base in Syria and infiltrated Israeli airspace. It carried out about 12 strikes targeting Syrian army and Iranian sites in Syria before Syrian air defenses shot down an F-16, marking the first time an Israeli jet was downed since 1982.
According to the Syrian government and its allies, the downing of the Israeli jet signals new rules of engagement in Syria, following more than 100 Israeli strikes that went without any retaliation.
"The new phase in the Syrian conflict makes the anti-ISIS war look like a stroll in the park. This has the potential to turn into a regional war," said Bilal Saab, an expert at the Washington-based Middle East Institute. ISIS is an alternative acronym for the Islamic State group.
U.S. WAR ON THE ISLAMIC STATE GROUP
The U.S. policy in Syria has always been vague and often inconsistent. But earlier this year, U.S. officials confirmed Washington's intention to keep troops indefinitely in northern Syria even after the defeat of IS. The U.S. says it seeks to prevent an IS resurgence as well as to counter Iranian influence in Syria.
But as IS shrinks, the estimated 2,000 U.S. troops stationed in Syria find themselves caught in a highly unpredictable and shifting battlefield, as demonstrated by an unexpected attack by pro-Assad fighters on U.S.-backed forces who were accompanied by U.S. advisers in Deir el-Zour.
The U.S. responded with a deadly barrage of bombs and artillery that U.S. officials say killed about 100 of the attackers. Russian news reports said Tuesday that an unknown number of private military contractors from Russia were among the dead, illustrating the risks foreign forces face on Syria's crowded battlefields.
Many of the U.S. troops in Syria are operating with local, Kurdish-dominated allies known as the Syrian Democratic Forces, in the eastern oil-producing Deir el-Zour region along the Euphrates River. The area had been a stronghold of IS militants until late last year.
But they are competing for control of Deir el-Zour with Russian-backed Syrian troops that are reinforced by Iranian-supported militias.
Keeping U.S. forces in areas that Assad's government hopes to reclaim inherently increases the probability of more clashes.
On Tuesday, Russia's foreign minister accused the U.S. of trying to create a quasi-state in eastern Syria.