Defense Secretary Jim Mattis said that whether the United States will launch further attacks against the Syrian regime will depend on whether Syrian President Bashar al-Assad uses chemical weapons again.

“That will depend on Mr. Assad,” Mattis said at a Pentagon briefing Friday night, when asked whether there would be more military operations, following U.S., French, and British strikes against Syrian chemical weapons facilities.

“Right now, this is a one-time shot. We believe it has sent a strong message to deter him from doing this again,” he told reporters. “Right now we have no additional attacks planned.”

Briefing alongside Mattis, Chairman of the Joint Chiefs of Staff Marine Gen. Joseph Dunford said Friday night’s strikes differed from those Trump ordered a year ago, after the Syrian regime conducted a chemical weapons attack in the Syrian town of Khan Sheikhoun.

While last year’s strikes were done unilaterally, and hit one target — a Syrian regime airfield that housed about 17 percent of its air force – Dunford said Friday’s strikes were conducted with two allies on multiple sites and would “result in a long-term degradation of Syria’s capability to develop chemical weapons.”

“Important infrastructure was destroyed. They will lose years of research and development data, specialized equipment, and expensive chemical weapons precursors,” he said.

“The strike was not only a strong message that their actions were inexcusable, but it has inflicted damage without unnecessary risk to innocent civilians,” he added.

He said the strikes — from U.S. ships and Air Force bombers — destroyed three targets that were specifically associated with the Syrian regime’s chemical weapons program.

Dunford said there were many targets to choose from, but they chose ones that would minimize the risk to innocent civilians.

The first target was a military scientific research center in the greater Damascus area – used for research, development, production and testing of chemical and biological weapons, he said.

The second target was a chemical weapons storage facility west of Homs that U.S. and allied officials assessed was the “primary location” of sarin production.

The third target was a facility for chemical weapons equipment storage and “an important command post,” he said.

He added that Russian forces were not given advance notice, though the airspace over Syria was conflicted with Russian air forces, as per normal procedures. The U.S. and Russia have a phone line through which they deconflict air operations so as to avoid in-air collisions and any other mishaps.

Deconfliction was part of the U.S.’s efforts to avoid hitting Russian forces in Syria that could lead to a military conflict in Syria between the two nations.

Mattis was reportedly concerned about hitting Russian and Iranian targets, but he said the U.S. and allies “specifically identified” targets to mitigate the risk of Russian forces being involved.

“We used our normal deconfliction channels. Those were active this week to work through the air space issues and so forth. We did not do any coordination with the Russians on the strikes, nor did we pre-notify them.”

Mattis also addressed the evidence showing that the Syrian regime had conducted the chemical weapons attack, amid allegations that it was fabricated and his own doubts expressed Thursday afternoon.

He said he became convinced Thursday, after he expressed those doubts.

“I am confident the Syrian regime conducted a chemical attack on innocent people in this last week. Absolutely confident. We have the intelligence level and confidence that we needed to conduct the attack,” he said.

He said the U.S. was “very confident” chlorine was used, but are “not ruling out” sarin use.

He said the president had Article II authority, allowing him to protect U.S. forces deployed to Syria. “We believe the president has every reason to defend vital American interests,” he said.

At the same time, he said, the U.S. had no intention to expand the strike further than chemical weapons-type targets.

“We were not out to expand this. We were very precise and proportionate, but at the same time, it was a heavy strike,” he said.

Despite concerns of retaliation, Mattis said Syrian surface to air missiles were used, but did not say whether they were destroyed, and said more details would be available in the coming day.

But he warned of retaliation via a “significant disinformation campaign.”

“Based on recent experience, we fully expect a significant disinformation campaign over the coming days by those who have aligned themselves with the Assad regime,” he said.