UPDATE 9 p.m.ET : President Trump announces joint air strikes with the UK and France against Syrian targets in retaliation for suspected chemical attack a week ago in Douma.

One year since the U.S. illegally launched 59 cruise missiles at Syrian government forces in response to an alleged chemical weapons attack, the Trump administration is preparing to take similar military action despite an increased risk of escalation that could lead to the start of a wider war.

The U.S., France, and Britain have been preparing to strike the Syrian government over the last several days, and Syria’s Russian patron has threatened the “gravest consequences” in response to an attack. Russia didn’t respond to last year’s one-off airstrikes, but Moscow isn’t likely to tolerate a larger U.S. attack carried out with other governments. Syria’s government and its allies seem more willing to fight back than they were a year ago, and that should give the Trump administration and our European allies pause. There is a greater risk of great power conflict erupting in Syria than there has been at any time since the end of the Cold War, and if Russian military personnel are killed by U.S. or allied strikes there is no telling how quickly things could deteriorate there and in other parts of the world.

President Trump’s public statements have strongly suggested that an attack will be happening soon, going so far as to taunt Russia on Twitter that they should “get ready” for the “new” and “smart” missiles that the U.S. would be using. Some members of Congress have insisted that the president lacks the legal authority to launch an attack on Syria without their authorization. As Sen. Tim Kaine (D-Virginia) put it, “[I]f this president can decide unilaterally to bomb Syria, I worry that he can make the same decision about North Korea or Iran or other nations. And these decisions are not supposed to be made without consultation and voting by Congress.” Unfortunately, Congressional leaders have shown no signs of wanting to hold a debate or have a vote before the attack takes place.

The Trump administration has not offered a public legal justification for last year’s strikes, and it seems unlikely to offer one this time. That is probably because there is no plausible interpretation of the law that permits the president to initiate hostilities against foreign governments on his own when the U.S. has not been attacked. There is no provision in international law that allows a U.S. attack on another government without explicit Security Council authorization, and we know that this authorization that will never be forthcoming in this case because of Russia’s veto. While the attack is being sold as the enforcement of a norm against chemical weapons use, it isn’t possible to uphold an international norm while violating the most fundamental rule of international law.

To date, the U.S. and its allies have presented no definitive evidence to support their claims against the Syrian government. It is entirely plausible that the Syrian government is guilty of using chlorine or sarin against its enemies and the civilian population, but there has been no real effort on the part of the U.S. and its allies to prove their accusation before deciding to act as executioners. Regardless, the U.S. and its allies have no authority to punish the Syrian government, and in doing so they may do significant harm to international peace and security.

A U.S.-led attack on the Syrian government could lead to war with Russia or Iran or both at once, and there is also a danger that it could help set off a war between Israel and Iran. Israeli Prime Minister Benjamin Netanyahu said earlier this week that Israel would not “allow” an Iranian military presence to be established in Syria. The prime minister’s threat came on the heels of Israeli strikes inside Syria that reportedly killed seven Iranians serving alongside the Syrian regime’s forces. Iran has threatened retaliation for the attack, and it has the ability through Hizbullah to make good on that threat if Israel carries out additional strikes. Israel might use a U.S.-led attack on Iran’s allies in Syria as an excuse to strike more Iranian targets, and Iran might then respond in kind with missile attacks on Israel. Lebanese, Syrian, and Israeli civilians would all suffer if that happened, and it would make an already chaotic international situation even worse.

It is a measure of how divorced from U.S. and allied security our Syria policy has become that our government is seriously preparing to launch another illegal attack on a government that hasn’t attacked us and doesn’t threaten us or our allies. Attacking the Syrian government won’t make the U.S. or any other country more secure, and it will likely weaken the government just enough to prolong Syria’s civil war and add to the suffering of the civilian population. It is a perfect example of a military intervention that is being done for its own sake with no connection to any discernible interests or strategy. No one stands to gain from such an attack except for the ideologues that have incessantly demanded deeper U.S. involvement in Syria for the last six years.

Daniel Larison is a senior editor at TAC, where he also keeps a solo blog. He has been published in the New York Times Book Review, Dallas Morning News, Front Porch Republic, and The Week. He holds a PhD in history from the University of Chicago. Follow him on Twitter.