The crises in the Middle East are beginning to join up and cross-infect each other. Israeli aircraft fired missiles at Syria’s T4 military airbase east of Homs early on Monday, just as other Israeli jets were making attacks on Gaza. President Donald Trump must decide whether or not he will order air strikes targeting Syrian government forces as a punishment for the alleged dropping of bombs filled with chlorine gas on a rebel-held part of the city of Douma in Eastern Ghouta that killed at least 40 civilians on Saturday night.

Trump will have difficulty not doing something impressive after denouncing “Animal Assad” and promising that the Syrian leader would “pay a price” for the gas attack. Trump has also denounced President Barak Obama for his timidity in his use of US military strength against President Bashar al-Assad, so the US may do something spectacular.

What is more doubtful is whether or not US air strikes will have much impact in the long term. In many respects, the political situation on the ground in Syria has gelled as Assad asserts his control over most of populated Syria. The last rebels are being evacuated from Eastern Ghouta on the outskirts of Damascus. Syrian troops and tanks are reported to be massing to overrun an Isis held stronghold in the south of the capital.

Eastern Ghouta bombings: Syrian war in pictures Show all 14 1 /14 Eastern Ghouta bombings: Syrian war in pictures Eastern Ghouta bombings: Syrian war in pictures A Syrian woman and children run for cover amid the rubble of buildings. AFP/Getty Eastern Ghouta bombings: Syrian war in pictures Smoke rises from buildings following the attack on the village of Mesraba in the rebel-held besieged Eastern Ghouta region on the outskirts of the capital Damascu. AFP/Getty Eastern Ghouta bombings: Syrian war in pictures Injured children receive medical treatment. EPA Eastern Ghouta bombings: Syrian war in pictures A Syrian man carries a child injured. AFP/Getty Eastern Ghouta bombings: Syrian war in pictures An injured child receives treatment following bombings on several areas of eastern Ghouta. EPA Eastern Ghouta bombings: Syrian war in pictures A child reacts inside a hospital after relatives were injured in the bombing. EPA Eastern Ghouta bombings: Syrian war in pictures Syrian children cry at a make-shift hospital in Douma following air strikes on the Syrian village of Mesraba. AFP/Getty Eastern Ghouta bombings: Syrian war in pictures Syrian Civil Defense group extinguishing a store during airstrikes and shelling by Syrian government forces. AP Eastern Ghouta bombings: Syrian war in pictures A wounded 12-year-old Syrian boy, cries as he receives treatment at a make-shift hospital. AFP/Getty Eastern Ghouta bombings: Syrian war in pictures Syrians carry a wounded man. AFP/Getty Eastern Ghouta bombings: Syrian war in pictures An injured man covered with blood at a medical point. Reuters Eastern Ghouta bombings: Syrian war in pictures People sit a medical point in the besieged town of Douma, Eastern Ghouta. Reuters Eastern Ghouta bombings: Syrian war in pictures Syrian Civil Defense running to help survivors. AP Eastern Ghouta bombings: Syrian war in pictures Injured children receive medical treatment. EPA

Syria is being divided into three zones of unequal size: Assad backed by Russia and Iran in much of the country; Sunni Arab factions backed by Turkey in Idlib, newly captured Afrin and territory north of Aleppo; and in the north and east, a large triangle of land east of the Euphrates held by the Kurds supported by 2,000 US troops able to call in massive air power. Even heavy US air strikes on a one-off basis will not significantly change this balance of power.

It remains mysterious why Assad should provoke the US and Europeans just at his moment of victory in Damascus and when the rebels are on the point of surrender or have already done so. Remarkably, the Russian foreign minister, Sergei Lavrov, says that Russian experts were able to enter the hospital in Douma where the chemical attack occurred – something which suggests the city has fallen – and interview eyewitnesses. He said: “Our military specialists have visited this place ... and they did not find any trace of chlorine or any other chemical substance used against civilians.” But the US state Department has said that Syrian forces are denying entry to international inspectors.

Donald Trump: 'nothing is off the table' for US response to alleged Syria chemical attack

Just because a poison gas attack at this stage would be an extremely stupid thing for the Syrian government to do, however, does not mean that they did not do it. As with many other atrocities in the Syrian war, there is always a residue of doubt about what really happened because of the lack of independent non-partisan reporting and investigation.

Trump is finding that there are limits to US power in Syria, which primarily depends on launching air strikes while the Kurdish People’s Protection Units (YPG) act as a mopping up force on the ground. But after the fall of their enclave at Afrin, the Kurds are mobilising to hold back the Turkish army and its Arab auxiliaries, many of them jihadis. In the long term, the Kurds are looking for a deal with Assad and have no intention of fighting him. In general, Trump’s instinct to get out of Syria is a sound one, and the interventionist ambitions of the Washington foreign policy establishment depend heavily on wishful thinking.

What makes the present situation potentially even more dangerous than it looks is the presence of various wild cards. Trump is clearly at odds with the Pentagon over a US military withdrawal from Syria, once Isis is finally eliminated. Nobody knows the final shape of US policy or whether it will finally take a concrete shape or remain fluid.

Washington could become more aggressive as the new national security adviser John Bolton and secretary of state Mike Pompeo take office. But the swift demise of their predecessors may argue that these super-hawks will have less leeway to exert their influence than they had hope and others feared.

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As for Israel, the latest crisis in Syria comes as a useful diversion from the escalating crisis in Gaza, but the latter is not going to go away. The two Israeli F-15s fired their missiles at T4 airbase from inside Lebanese airspace, showing a degree of caution. As Assad becomes stronger and gains control of more and more of Syria, Israel will want to flex its military muscles but this does not necessarily mean that Israel wants to fight a war with Syria or Hezbollah, despite the belligerent rhetoric on all sides.