Mr. Trump posted dozens of tweets about the conflict in the years before he declared his candidacy for the White House, and frequently did so during the campaign as well. Channeling the same bluntness that helped fuel his political rise, he carved out a staunchly noninterventionist stance on the conflict and criticized as plodding Mr. Obama’s approach.

But he also made one thing clear: If he was in charge, any action would be swift and secretive to catch Mr. Assad off guard.

We have sifted through Mr. Trump’s account for the highlights:

2011-2012: Syria enters his radar screen

It was several months after it began before the growing conflict in Syria appears to have attracted Mr. Trump’s attention, and, even then, it was only a blip. Mr. Trump, at the time best known as a reality television personality, first weighed in on Syria in October 2011 to criticize the United Nations for its inaction after China and Russia had successfully blocked sanctions against the Assad government.