Trump reportedly deferred to Mattis’ advice  and ordered a smaller attack on Syria than he and Bolton had originally wanted:
President Donald Trump deferred to his Pentagon chief’s caution and tempered his preference for a more robust attack on Syria over allegations it used deadly gas on civilians, the first hints at the direction of his revamped national-security team.
It is better that Mattis’ view prevailed over Bolton’s, but one problem with taking any military action in response to demands to “do something” is that there will always be a chorus of hard-liners demanding that the U.S. “do more” than it already has. Once a president has conceded that military action is an appropriate response to a foreign government’s behavior, he has put himself in a trap of his own making. When the first strikes don’t “work” or are deemed to be inadequate to “get the job done,” the pressure to escalate increases. Since Trump is especially sensitive to accusations of looking “weak,” he is probably more likely than most presidents to listen to the hard-liners that fault him for not doing enough in Syria. It makes me wonder how long Mattis can hold off the president when Bolton is going to keep agitating for more aggressive actions.
Marc Thiessen complains  that Trump should have done far more than he did:
But let’s be clear: Friday night’s strikes were “just muscular enough not to get mocked.” As a result, they did more damage to the United States’ credibility on the world stage than they did to the Assad regime [bold mine-DL].
Hawks invoke “credibility” when they want to attack someone, and then even when the attack happens they will claim that it undermines “credibility” because it wasn’t big enough. Following through on unnecessary threats with illegal military action isn’t enough for the “credibility”-obsessed, because they are simply using “credibility” as an excuse to plunge the U.S. into more conflicts. If a limited U.S. military action doesn’t get them that, they will insist on more and bigger attacks until they get the war they want. While sane people everywhere were relieved that last week’s attack was small and didn’t provoke retaliation, quite a few hawks were dismayed for the same reasons.
Far from being chastened, the U.S. response will embolden Assad, Russia and Iran. And it will embolden other U.S. adversaries as well.
Trump’s attack on Syria last week was illegal and useless, but it is very doubtful that it will have the effect Thiessen describes here. The people that use the bogus “credibility” argument don’t understand how states actually judge these things  in the real world, and so they always predict that any action that isn’t aggressive enough for them will “embolden” every adversary in the world. Curiously, this never happens, and the people obsessed with “credibility” are never held accountable for their shoddy analysis. Just as the so-called “red line” episode didn’t make U.S. adversaries more aggressive than they already were, this attack will have no discernible effect on their behavior, either. The danger is that the president listens to some version of these garbage arguments and concludes that he needs to “do more” by launching larger attacks.