Story highlights President Trump succeeded in his first military strike on a Syrian airfield

Juliette Kayyem: However, his lack of a defined foreign policy is deeply unsettling

"Keep them guessing" is not a presidential doctrine, it's a lack of foresight, writes Kayyem

CNN national security analyst Juliette Kayyem is the author of the best-selling "Security Mom: An Unclassified Guide to Protecting Our Homeland and Your Home." She is a professor at Harvard's Kennedy School, a former Assistant Secretary of Homeland Security in the Obama administration, host of the national security podcast The SCIF and founder of Kayyem Solutions, a security consulting firm. The opinions expressed in this commentary are hers.

(CNN) The elusive search for a "Trump Doctrine" in foreign affairs was made more pressing after the US president authorized the launch of a missile attack in Syria in response to President Bashar al-Assad's apparent use of chemical weapons against his people.

The images of children gasping for air and dying in their parents' arms are said to have made Trump, who came to power on an "America First" isolationist doctrine, react.

It's possible that Trump was so moved by the images that the strikes were merely an emotional response to a moral outrage. But the president's emotions are not a strategy, and America's forces cannot be aligned around what does, and does not, move him.

Juliette Kayyem

Our role is to act in ways that balance the reasons for our action against the consequences that will occur when other nations -- equally proud, defiant and powerful -- respond.

And though immediate responses to the strike were overwhelmingly positive, and in some instances fawning, the fog of war tends to get lifted. In a show of defiance, Syria has already started utilizing the same airfield the US military struck. Russia has made moves to withdraw some operations from the uneasy but important US-Russian alliance to combat ISIS. And the US has reduced airstrikes against ISIS as it determines what Russia's response will be.