"The biggest difference that Trump and his commanders confront now is the presence of Russian troops on the battlefield and Russian air defense systems that are capable of shooting down U.S. planes. Today, Russian troops are intermingled with Syrian forces, and any strike on a Syrian military target could also produce Russian military casualties.
Retired Gen. John Allen, who coordinated the campaign against the Islamic State in Iraq and Syria during the Obama administration, said that the military strikes could have had a “decisive” impact on the war had they been launched in 2013. He described Obama’s decision not to strike as devastating.
“It is much harder now,” Allen said. “The United States has to ask itself a question: How angry do we want to be on this issue? Are we enraged enough morally that we are ready to take action even with the possibility of dead Russians?”