Mission accomplished!” The presidential tweet was beyond ominous, reprising as it did George W Bush’s ill-fated banner 15 years ago. As his Iraq war dragged on its bloody course, Bush later admitted it had “conveyed the wrong message”. Now Trump’s crass ignorance of history should serve as a warning he may be destined, or “locked and loaded”, to repeat it.

Theresa May has tied this country to his fickle whims. Inside Donald Trump’s circus, war breaks out between James “Mad Dog” Mattis, the defence secretary who emerges as the sanest in that shape-shifting entourage, and Trump’s terrifying new national security adviser, John Bolton, who reportedly wanted to bomb the hell out of Iranian forces while they were at it on Friday night, urging the president to cancel the Iran nuclear deal. This is where May’s hand-holding has left us: hitched to these dangerous men. What a political risk she has taken, out there alone, against public opinion both before and after the bombing: an instant Survation poll finds 40% against, 36% in favour. Even more striking, 54% say she was wrong not to consult parliament, with only 30% backing her on that.

Theresa May faces anger over Syria raids as Trump declares ‘mission accomplished’ Read more

Today she finally faces the MPs she dared not consult – Labour, SNP, Lib Dems and prominent Tories including Ken Clarke, Dominic Grieve and former soldier Bob Seely, who loudly expressed their doubts beforehand. The only reason to avoid parliament was fear of losing a vote, as David Cameron did in 2013. Some in the cabinet are reported to have argued to let parliament vote first – David Davis among them. Will there be a posthumous vote? The chief whip, Julian Smith, is sounding out his backbenchers to see if the government would win, with Tornadoes safely returned. There will be a vote only if he has the numbers. So no vote today means parliament would certainly have rejected firing off those Friday night missiles.

May will bear all responsibility for whatever comes next, with support from neither people nor MPs to protect her from any fallout. The Russian UN ambassador, Anatoly Antonov, warns: “Such actions will not be left without consequences.” Empty threat? We wait to see, fearful of cyber-attack on the national grid, the NHS or anything else. GCHQ says it’s on “high alert” to cyber-retaliate “proportionately”. Some fear Putin will release fake news or genuine kompromat, revealing compromising stories about British figures: consider the damage done to Hillary Clinton by releasing her emails. Downing Street promises more sanctions against Putin-allied oligarchs’ “illicit finances”. (Why not years ago?) Perhaps she will be lucky – but she is not a lucky prime minister.

The two most dangerous words in politics are “Do something!” Doesn’t matter what, but “something must be done”. Politicians need to demonstrate effectiveness, so it takes exceptional honesty to say nothing can be done, or doing something risks making things worse. The splurge of righteous indignation filling the newspapers this weekend declared the undoubted truth that Assad is a monster gassing his own people. The Russians and Iranians are monstrous for letting him flout the 1928 Geneva convention. But there is nothing to be done. He will win this war. Chemical attacks were effective, as rebels fled Douma. Will May take in those refugees?

Watching it happen, hand-wringing and helpless, is the price we pay for disastrous Iraq and Afghanistan interventions. But what a small price compared with the Syrians – over 500,000 dead, 2 million injured, 5 million fled abroad and 6 million displaced in their own country. Conventional weapons did this, so going to war over the 75 dead from chlorine gas looks quixotic – a vaingloriously pointless gesture. What ifs are unknowable, but if we had never attacked Iraq, would we have intervened in Syria early, with gusto? We seem to have learned the lesson that western democracies don’t have the staying power to defeat distant dictators who are no direct threat. Do what we can – Kosovo, Sierra Leone – but it’s futile for Britain to pretend to an ethical, world-policing foreign policy, while we are supplicants to Saudi Arabian buying power despite Yemen. Firing ineffective missiles may boost post-Brexit delusions, but in truth only makes us look weaker to the world.

Tomahawk strikes and smouldering ruins – but no real change in Syria Read more

The drumbeats of even an unpopular war stir macho satisfactions: look at the relish lavished on war-porn pictures of bunker-busting hardware, those warships, subs, Tomahawks and Storm Shadows. How frivolous to deploy all this with no intent of altering Syria’s abysmal future, while causing a perilous confrontation with Russia, old cold war understandings replaced with the unpredictable swagger of new, trigger-happy leaders.

Leaders see a beautiful clarity in faraway war compared with the fog of home. So Trump escapes his special investigator, Macron his multiple strikes, May her car-crash Brexit. Give them a “fit for purpose”, saluting general and a noble cause, and everything looks easier. Almost always, Britain follows the US, whatever party here, whatever president there. Brexit makes us vulnerable, anxious to prove we still have friends. Trump’s early, anti-Nato bombast reminds us Europe relies entirely on US defence – and Putin threatens. That realpolitik is the one good reason for obsequiousness. But surely the real-world Iraq catastrophe should have warned us off by now.

Jeremy Corbyn is right – though some say, sourly, he is just a stopped clock. But his brand of being right hasn’t helped him: Survation’s poll finds him 20 points behind May on “Who is best in an international crisis?” Corbyn, and all of us who oppose this attack, are in unsavoury company, with Marine Le Pen (loaned Russian cash), ultra-right Matteo Salvini of Italy’s Lega, and the Morning Star. But if parliament gets a vote today, Labour anti-Corbynites should put that aside, remember Iraq, and focus on the question itself. This was a reckless, fruitless, unpopular and incredibly dangerous gesture that may yet have “consequences”. Shouldn’t MPs have voted first?

• Polly Toynbee is a Guardian columnist