Mr. Trump, who has made it a central goal of his presidency to improve strained ties with Moscow even amid criticism of Russian meddling in last year’s election, found that goal now at risk as both sides traded harsh words in a diplomatic confrontation reminiscent of the darkest moments of the last few years.
President Vladimir V. Putin’s office called the missile strike on Syria a “significant blow” to the Russian-American relationship, while Trump administration officials suggested Russia bore some responsibility for the chemical weapons attack on Syrian civilians that precipitated the American response.
The missile strike demonstrated the potential dangers of Russian and American forces’ operating in proximity, and American military planners acted to avert a direct conflict. Fewer than 100 Russian troops deployed in support of the Syrian government of President Bashar al-Assad were believed to be stationed at the Syrian air base targeted by American forces. An American official said the Russians on the ground were given just 60 to 90 minutes of advance notice that the cruise missiles were coming and were not advised whether to take shelter or flee.
Although Russia did not deploy its air defense system in Syria against the American cruise missiles, it flexed its military muscles after the attack. Russia said it would bolster Syria’s air defenses, while the Russian news agency Tass reported that a frigate would enter the Mediterranean Sea on Friday and would visit the logistics base at the Syrian port of Tartus.