WASHINGTON — In sending missiles and bombs at Syria, President Trump hit more targets and used more firepower than he did in a similar military strike last year. But in the end, he opted for what was still a restrained operation that was evidently calculated to avoid provoking Syria’s patrons in Russia and Iran into retaliating.

The United States and its European allies chose three targets instead of the single air base hit last year and used twice as many weapons. Still, American officials said the attack was intended as a proportional strike aimed specifically at Syria’s chemical weapons facilities rather than a broader set of targets and was a one-time, one-night assault to punish Damascus for a suspected gas attack last weekend.

In the days before the strike, Defense Secretary Jim Mattis cautioned against a quick assault without a more thought-through strategy. He expressed concern about the potential for escalating the conflict by drawing Russia and Iran into a deeper confrontation with the United States in a country where all three have forces on the ground. With Russian and Iranian forces supporting the government of President Bashar al-Assad, the potential for miscues weighed on military planners.

For all of Mr. Trump’s tough language this week, the variant he chose made no apparent effort to damage Mr. Assad’s broader war machine or his government’s command and control of its forces beyond its chemical weapons. The one-night burst of ordnance appears unlikely to change the overall balance of forces in Syria seven years into its bloody civil war. But the president hoped it would be enough to deter Mr. Assad from using chemical weapons again without being so damaging as to compel Russia and Iran to intervene.