President Donald Trump had little option but to order a missile strike against a Syrian airbase after holding Syria responsible for that poison gas attack on Khan Sheikhoun that killed 80 civilians. He had criticised President Obama for being weak, slow and indecisive when facing similar challenges, so he could scarcely do nothing when President Bashar al-Assad appeared to breach the agreement in 2013 to hand over all his chemical weapons to be destroyed.

The fact that the US has taken its first direct military action against Assad is significant, not so much because it has done much damage to the Syrian armed forces, but because it may be repeated. Senior politicians and generals in the US have been calling for air strikes to take out or at last “ground” the whole Syrian air force. This option is now more on the table than it was previously, but that does not mean that it is going to happen.

The launching of 59 Tomahawk missiles that killed six people and did an unknown amount of damage at al-Shayrat airbase in Homs province in central Syria is symbolic. But it is a warning that is likely to be taken seriously in both Moscow and Damascus, because full-scale American intervention against Assad is the one thing that would deny them victory in the war.

Those who argue that the Syrian armed forces would not have done anything quite so foolish and against their own interests as to launch the strikes, probably underestimate the extent of the stupidity present in all armies. There is an old Israeli military saying, employed about a number of their commanders, which is apposite and says that the general “was so stupid that even the other generals noticed”.

Despite the air strike overnight, the Assad government and the Russians remain in a strong military position because they control all the biggest cities in Syria since the capture of east Aleppo in December. The number of Syrians still in Syria is probably about 16 million, assuming there are five or six million refugees, and of these 10 million are in areas under Assad’s control and two million apiece in zones held by Isis, the non-Isis armed opposition and the Syrian Kurds. The Syrian Kurds remain a powerful force, but the Isis and al-Qaeda armed opposition movements are crumbling.

In pictures: US missile strike against Syria Show all 7 1 /7 In pictures: US missile strike against Syria In pictures: US missile strike against Syria The guided-missile destroyer USS Porter (DDG 78) launches a tomahawk land attack missile in the Mediterranean Sea AP In pictures: US missile strike against Syria The United States military launched at least 50 tomahawk cruise missiles at al-Shayrat military airfield near Homs, Syria, in response to the Syrian military's alleged use of chemical weapons in an airstrike in a rebel held area in Idlib province EPA In pictures: US missile strike against Syria Shayrat airfield in Syria Getty Images In pictures: US missile strike against Syria US Navy guided-missile destroyer USS Ross (DDG 71) fires a tomahawk land attack missile in Mediterranean Sea Reuters In pictures: US missile strike against Syria US Navy guided-missile destroyer USS Ross (DDG 71) fires a tomahawk land attack missile in Mediterranean Sea Reuters In pictures: US missile strike against Syria President Donald Trump speaks at Mar-a-Lago in Palm Beach, Fla., after the US fired a barrage of cruise missiles into Syria in retaliation for this week's gruesome chemical weapons attack against civilians AP In pictures: US missile strike against Syria Syria's President Bashar al-Assad Reuters

The exiled anti-Assad opposition, who have little strength on the ground in Syria, has welcomed the US missile strike, saying it ended Assad’s “impunity”. They have called for more of the same, but if this does not happen – and it is unlikely that they will – then the political and military balance of power in Syria will not change significantly.

The war is by no means over, but it has jelled and it is getting towards the endgame. It is very unlikely that Washington will want to change its present level of engagement to the point that it became involved as it did – with disastrous results for all concerned – in Afghanistan in 2001, Iraq in 2003 and Libya in 2011. The White House contrasted overnight its swift and decisive response to Assad’s use of chemical weapons with the supposed feebleness of President Obama but, in reality, the policies of both administrations are much the same.

Obama was giving priority to eliminating Isis and the al-Qaeda-type movements that dominate the armed opposition and Trump is doing likewise. Obama had long ago placed getting rid of Assad on the back burner and the same is more publicly true of Trump, or so it seemed until the chemical attack on Khan Sheikhoun in Idlib province on Tuesday. Secretary of State Rex Tillerson was much criticised by interventionists in Washington for saying a few days earlier that “the fate of Assad was in the hands of the Syrian people” or, in other words, the Syrian leader was going to stay.

Syria: What led to the US airstrikes?

Trump said that Tuesday’s suspected chemical gas attack had changed his attitude towards Assad and developments in Syria. But this is doubtful as American policies will probably stay the same because they are working successfully and the self-declared Islamic State is getting weaker by the day. The Iraqi armed forces have suffered heavy losses – perhaps 6,000 dead and wounded – in the battle for Mosul, but they will eventually capture it. The US-backed Syrian Kurdish advance on Isis’s de facto Syrian capital at Raqqa is likely to succeed in taking it.

The US alliance with the Syrian Kurds and the Russian alliance with Assad are defeating Isis and the al-Qaeda clones in Syria. This is different from in the past when Isis’s many enemies detested each other as much, if not more, than they hated the salafi-jihadi extremists they were supposedly fighting.

The US will probably not want to let Isis and al-Qaeda off the hook now by weakening the Syrian armed forces that remain the strongest military power in Syria. At the same time, the Americans do not intend to allow Assad to flaunt his success and, even before the chemical attack, there were reports of the US resuming aid to some opposition groups deemed to be anti-jihadi and anti-Assad.

As for the Russians, their military intervention in Syria has hitherto been highly successful because it has re-established them, at least in the Middle East, as a superpower. If they conclude that Assad was indeed behind the chemical attack – something they currently deny – then they will be infuriated that he has risked so much for so little. The Kremlin will be eager to continue to pursue parallel policies with Washington, something that dates back to 2015 when Obama decided not to oppose Putin’s military intervention on the side of Assad. This was a critical moment in the outcome of the war.