Four years ago, massive citizen opposition and mobilization stopped a possible U.S. military attack on the Assad government of Syria that many predicted would have made the terrible conflict even worse. Once again, we need to stop an escalation of that dreadful war and instead use this tragedy as an impetus for a negotiated settlement.

In 2013 President Obama’s threat of intervention came in response to the horrible chemical attack in Ghouta, Syria that killed between 280 and 1,000 people. Instead, the Russian government brokered a deal with the Assad regime for the international community to destroy its chemical arsenal on a U.S.-provided ship. But UN investigators reported that in 2014 and 2015, both the Syrian government and Islamic State forces engaged in chemical attacks.

Now, four years later, another large chemical cloud has killed an estimated 70 people in the rebel-held town of Khan Sheikhoun, and President Trump threatened and has initiated military action against the Assad regime already, with tomahawk missile strikes on a Syrian Government airport.

The U.S. military is already heavily involved in the Syrian quagmire. There are about 500 Special Operations forces, 200 Rangers and 200 Marines stationed there to advise various groups fighting the Syrian government and ISIS, and the Trump administration has been contemplating sending 1,000 more troops to fight ISIS. To bolster the Assad government, the Russian government has mobilized its largest military deployment outside its territory in decades.

This recent chemical attack is just the latest in a war that has taken the lives of over 400,000 Syrians. If the Trump administration decides to escalate US military involvement by bombing the Syrian government’s power centers of Damascus and Aleppo and pushing rebel fighters to hold territory for a new government, the carnage—and chaos—will increase.

Just look at recent U.S. experience in Afghanistan, Iraq and Libya. In Afghanistan after the fall of the Taliban, various militia factions that the U.S. government had supported raced to Kabul for control of the capital and their fight for power in successive corrupt governments has led to the violence that continues 15 years later. In Iraq,the Project for the New American Century (PNAC) government-in-exile, led by Ahmed Chalabi, disintegrated and the U.S.-appointed Pro-Consul Paul Bremer so mismanaged the country that it provided the opportunity for ISIS to fester in American-operated prisons and develop plans to form its caliphate in Iraq and Syria. In Libya, the U.S./NATO bombing campaign “to protect Libyans” from Qaddafi resulted in a country split in three parts.

Would U.S. bombing in Syria lead us into a direct confrontation with Russia? And if the U.S. was successful in toppling Assad, who among the dozens of rebel groups would take his place and would they really be able to stabilize the country?

Instead of more bombing, the Trump administration should pressure the Russian government to support a UN investigation into the chemical attack and take bold steps to seek a resolution of this dreadful conflict. In 2013, the Russian government said it would bring President Assad to the negotiating table. That offer was ignored by the Obama administration, which felt it was still possible for rebels it supported to overthrow the Assad government. That was before the Russians came to the rescue of its ally Assad. Now is the time for President Trump to use his “Russia connection” to broker a negotiated solution.

The U.S. and Russian militaries already have daily contact to sort out airspace for bombing the parts of Syria each wants to incinerate. Senior military officials from both countries met last month in Turkey, a country that has shot down one Russian jet and which hosts U.S. aircraft that bomb Syria. Instead of collaborating to carve up airspace, the U.S. and Russia should be meeting figure out how to impose a ceasefire.

In 1997, National Security Advisor General H.R. McMaster wrote a book called “Dereliction of Duty: Johnson, McNamara, the Joint Chiefs, and the Lies That Led to Vietnam” about the failure of military leaders to give an honest evaluation and analysis to the president and other senior officials in the 1963-1965 lead-up to the Vietnam War. McMaster denounced these powerful men for “arrogance, weakness, lying in pursuit of self-interest and abdication of responsibility to the American people.”

Can someone in the White House, NSC, Pentagon, or State Department please give President Trump an honest assessment of the history of U.S. military actions over the past 15 years and the likely outcome of further US military involvement in Syria?

General McMaster, how about you?

Call your members of the U.S. Congress (202-224-3121) and the White House (202-456-1111) and demand U.S. negotiations with the Syrian and Russian governments to end the carnage.