I trust the prime minister. Theresa May’s caution is admirable compared with Vladimir Putin’s macho conduct or the infantile tweeting of Donald Trump. I also understand that our alliances dictate that she now has to support the US and France – in some way – if action is taken against Bashar al-Assad’s regime. They have recently supported the UK over the poisoning of Sergei Skripal.

However, serving in military campaigns, as I have done in Afghanistan and Iraq, one sees both the utility and the futility of force. Success lies in recognising the difference. Bombing the Assad regime makes ethical sense, but I have seen no evidence to show it makes strategic or practical sense.

Here’s why I’m a sceptic. First, Assad has won. Supported by Russian airpower and Iranian/Hezbollah military advisers and soldiers, his forces are mopping up pockets of opposition. Bombing would not change that basic fact. It might prevent him using chemical weapons for a period. But Assad will continue to kill his own people using different means, such as barrel bombs.

Second, the Douma attack was the 34th recorded use of chemical weapons in Syria. At least two dozen attacks have been blamed by the UN on the regime. All but one have gone unpunished, and that punishment changed little.

That doesn’t make the use of chemical weapons OK. They are despicable weapons designed to spread fear. To win a war, you need to control territory and govern. Chemical weapons on civilian targets cause mass panic, forcing populations to flee, “weaponising” displaced persons, if you like. But let us be honest with ourselves, we are in danger of being seen to act now because we are reacting to a tweet.

The time to have acted was in 2013. Assad was weaker. Syrian opposition moderates had more sway. The Russians weren’t in the country. Shamefully, Labour’s leader, Ed Miliband (remember him?), tried to play politics with disastrous results. Parliament voted no.

Third, we are on weak ground, legally and physically. US, UK and French forces in Syria are not there at the invitation of the Assad regime, but to defeat Isis, which has been largely done. Assad’s is the legally recognised government, however much we wish it wasn’t. Assad, backed by Russia and Iran, will order the US and its allies out. Pressure will grow. We will have to leave anyway. When we do, Russia will claim it threw us out.

There is a theory that we are being led into a trap. Putin wants us to act because in Syria he and Iran are strong, the US and its allies weak. It is not impossible that the Kremlin would welcome the deaths of Russian soldiers. They would instantly become martyrs, opposition in Russia to Putin would become ever more difficult and it would give the president carte blanche at home and abroad.

Fourth, talk to Syrians and they’ll say: we are being killed in our hundreds by barrel bombs, what’s the difference how we die?

Fifth, the opportunities are modest. Either the US bombs a little, like last time, and it doesn’t make much difference, or the US bombs a lot – and risks armed confrontation with Russia.

And that’s the biggest point. The dangers are profound. There is a chance of war now with Russia. I do not make moral equivalence between the US administration and the Kremlin, but both leaders seem to be thinking with their egos. Expect threats of war – and even nuclear war – from Russia if bombing takes place.

There is an unstable dynamic between Saudi Arabia and Iran, which have backed different sides in Syria. Ditto Israel and Iran. Any of these actors could complicate the situation further. And our relationship with Moscow will be poisoned. Putin and the Russian security elite appear to believe that the west brought down the USSR and have tried to impoverish Russia ever since. They behave as if they want to replay the cold war and have been preparing for conflict in difference theatres: in cyberspace, they have repeatedly broken through western defences and penetrated the US National Security Agency. In eastern Europe, Russia is aiming for conventional dominance, and in the rest of Europe for missile dominance and tactical nuclear dominance. They are masters of information and subversive warfare. In the Balkans the Kremlin has been arming the Bosnian Serbs, in Afghanistan it has been allegedly arming the Taliban.

We need to understand Russian warfare and act to defend ourselves. Instead, we are in danger of stumbling into using lethal force without thinking through the consequences. Even if we get through the next few weeks without actual conflict between Russia and the west, the new cold war will have become considerably hotter for the next few years. Without a coherent and articulated strategy the western alliance risks “gesture bombing”. To paraphrase the great Chinese military thinker Sun Tzu, war without strategy is noise before defeat.

• Bob Seely is a Conservative MP