Russian President Vladimir Putin, center. (Mikhail Klimentyev/RIA-Novosti, Kremlin Pool Photo via Associated Press)

PRESIDENT OBAMA’S response to Russia’s military campaign in Syria increasingly appears to boil down to “let them have it.” Mr. Obama has taken to lecturing Vladi­mir Putin that he is making a mistake that will result in a “quagmire,” while publicly assuring him that the United States will do nothing to contest the concerted assault the Russian president has launched against Syrian rebels, including those who have been trained and supplied by the United States. “We’re not going to make Syria into a proxy war between the United States and Russia,” Mr. Obama says. That sounds like a green light for Moscow to eliminate any alternative in Syria to the regime of Bashar al-Assad and the Islamic State, or ISIL.

On Friday, the administration signaled a further retreat, announcing that it is abandoning a Pentagon program to recruit and train new Syrian forces. The program was doomed by the White House’s insistence that the units not be supported against the Assad regime, or even defended against it. “When we tried to get them to just focus on ISIL, the response we’d get back is, how can we focus on ISIL when every single day we’re having barrel bombs and attacks from the regime?” Mr. Obama conceded at his Oct. 2 news conference. This should not have been a revelation: The White House ignored the many critics in and outside of Congress who foresaw that outcome from the training program’s inception.

Mr. Obama responded to Russia’s invasion of Ukraine by predicting it would be self defeating; 20 months later, Mr. Putin controls Crimea and a slice of eastern Ukraine and has won Western agreement for a political settlement that, if fully implemented, will cripple Ukraine’s democratic government. Now the White House suggests that Moscow’s offensive in Syria will also fail on its own. In the long run, that may be the case. But Mr. Obama’s policy risks a host of near-term catastrophes, from the further strengthening of the Islamic State to the elimination of any prospect of a Syrian political solution.

The president appears to have decided on a course of stepping up U.S. support for existing Syrian forces fighting the Islamic State in the eastern part of the country, including Kurds and Sunni tribes. “Equipment packages and weapons” will be provided “to a select group of vetted leaders and their units,” a Pentagon statement said Friday, “so that over time they can make a concerted push into territory still controlled by ISIL.”

Such an offensive toward the Islamic State capital of Raqqa would be welcome. But, combined with Mr. Obama’s refusal to assist the U.S.-allied forces now being pummeled by Russian missiles, it would have the effect of creating, de facto, the “coalition” Mr. Putin has been calling for, in which the United States and its allies join with Russia in fighting all forces that oppose the Assad government. It would force moderate Syrians who oppose the regime into the arms of the Islamic State and advance Mr. Putin’s aim of restoring Russia as a power in the region at U.S. expense.

The United States need not go to war with Russia in order to take steps that counter Mr. Putin and preserve vital U.S. interests. Assistance to moderate forces fighting the Assad government should be accelerated: The rebels desperately need more U.S. antitank missiles. A safe zone should be established in northern Syria, in cooperation with Turkey, where civilians can be protected. Instead of lectures, Mr. Putin ought to be given red lines; without them, his aggression will escalate.