Before 59 cruise missiles crashed down on a Syrian air base, U.S. officials forewarned their Russian counterparts of the impending attack.

The U.S. air attack sent a clear message to President Bashar al-Assad: The use of chemical weapons will be met with U.S. force.

“If the intent of the (Trump) administration was to send what I would call a strategic signal then they’ve done that,” said Former U.S. Ambassador to Syria and Director of Rice University’s Baker Institute for Public Policy, Edward Djerejian.

Friday afternoon, the United States and Russia volleyed over whether they will maintain the line of communications that prevent midair collisions of warplanes in Syria. It’s the same hotline U.S. officials warned the Russian’s with before the air strike.

Djerejian says decisions like this will be determined by what the U.S. does next, during what he calls ‘the day-after effect.’

“The bid question is, is this a single action? Will there be a follow up, and if so, under what circumstances?” Djerejian said. “And the third and the big question is what is the long-term strategy?”

Avoiding conflict with Russia, who supports Syria’s Assad, while keeping a hard stance against chemical warfare is the President’s next task in Djerejian’s playbook.

“The first step is to build on this and get an international coalition of the willing that will stand together and send a strong signal to leaders like Bashar al-Assad that don’t take this path there’s a price to pay,” Djerejian said.

In a related development, U.S. officials also said they’re aware of Russians with chemical weapons expertise who have been in Syria.