On April 9, Iranian and Russian military chiefs said President Trump crossed a "red line" with his missile attack against the Assad regime in Syria.
"From now on we will respond with force to any breach of red lines and America knows our ability to respond well," they announced, reported the Daily Mail.
The Russian Embassy in London further warned that there would be a "real war" if Washington gives Moscow an ultimatum over Syria.
President Vladimir V. Putin’s office called the missile strike a “significant blow” to the Russian-American relationship, while Prime Minister Dmitri A. Medvedev said the attack had “completely ruined” it, reported The New York Times.
The crisis began on April 4, when the Syrian government allegedly attacked the town of Khan Sheikhoun, an anti-government stronghold, with sarin gas. At least 87 people died in the attack.
On April 6, Trump ordered the bombing of the Al Shayrat airfield in western Syria, where the chemical weapons attack originated, in retaliation.
Although Trump's decision has received strong bipartisan support in the U.S., it does have its critics.
Sen. Rand Paul condemned it, reported CNN. "We have to decide when we are going to intervene as a country, when we are going to put our young men and women, put their lives on the line," Paul argued. "And we don't, frankly, do it for every atrocity in the world. It doesn't mean we don't have great sympathy, but we have to debate when and where we go to war. That's what our founding fathers asked us to do."
When former President Obama contemplated retaliating against the Assad regime in 2013 after an even deadlier sarin attack, Donald Trump weighed in on Twitter: "The President must get Congressional approval before attacking Syria -- big mistake if he does not!” He also tweeted: “Stay out of Syria.”
Obama did indeed follow the constitutional requirement and consulted Congress, which refused to give him authorization to take action. At the time, Trump said the result "may have saved us from doing a horrible and very costly (in more ways than money) attack on Syria!"
This time, however, Trump claimed that pictures of children who were victims of the sarin attack touched his heart and moved him to take action.
In response, the conservative journal National Review argued that going to war for sentimental reasons is not an adequate justification.
Stephen Zunes, a professor of politics and international studies at the University of San Francisco, accused Trump of hypocrisy. Writing in The Progressive, Zunes pointed out that the president's proposed budget makes major cuts to programs that have provided relief to Syrian refugees fleeing the violence of the Assad regime.
In addition, he observed that since Trump came to office, nearly 1,000 civilians have been killed by U.S. airstrikes in Syria and Iraq -- including 60 civilians last month near the site of last week's sarin attack.
The League of Nations in 1925 adopted the Geneva Protocol -- an international treaty that prohibited the use of chemical and biological weapons. However, the U.S. did not ratify it until 50 years later, according to the State Department.