His work over three decades has appeared in The Atlantic, The Washington Post, The New York Times, The New Republic, The National Interest, Foreign Affairs and The Wall Street Journal, among other publications.

He has lectured at military war colleges, the FBI, the National Security Agency, the Pentagon's Joint Chiefs of Staff, major universities, the CIA, and business forums, and has appeared on PBS, NPR, C-SPAN, and Fox News.

In 2006–08, Kaplan was a visiting professor at the United States Naval Academy, Annapolis, where he taught a course called "Future Global Security Challenges".

He first worked as a freelance foreign correspondent reporting on Eastern Europe and the Middle East, but slowly expanded his coverage to all regions ignored in the popular press.

For The New York Times, reviewer Richard Bernstein wrote that Kaplan "conveys a historically informed tragic sense in recognizing humankind's tendency toward a kind of slipshod, gooey, utopian and ultimately dangerous optimism.

Kaplan, along with Fareed Zakaria of Newsweek, has been described by American pundit Glenn Greenwald as one of many prominent journalists advocating support for the Iraq War.

[9] Kaplan participated in a secret meeting convened by the then Deputy Secretary of Defense Paul D. Wolfowitz, at which he helped draft an internal government document advocating the invasion of Iraq.

[11][12] In his 2023 book The Tragic Mind: Fear, Fate, and the Burden of Power, Kaplan writes that he suffered from clinical depression due to the loss of American and Iraqi lives he believed his support for the Iraq War indirectly caused.

[13] Similarly, he expresses difficulty grappling with the impact of his book Balkan Ghosts, which he believes led the Clinton administration to neglect the genocide in southeastern Europe.

[15] He has drawn parallels between Trump's focus on a militaristic image and large reductions to "soft" non-military foreign policy efforts with the gradual decline of the Roman Empire as a result of similar excess.

[16] In The Tragic Mind: Fear, Fate, and the Burden of Power, Kaplan expresses disillusionment with neoconservative foreign policy, in particular the idea of democracy promotion through military force.

[17] He argues that politicians can benefit from a humanistic understanding of Shakespearean and Greek tragedy to prevent neoconservatism and ideological foreign policy from causing significant loss of life or resources.

Kaplan predicts that the age of mass infantry warfare is probably over and writes that the conflict in Iraq caught the United States Army between being a "dinosaur" and a "light and lethal force of the future."

Kaplan's book Hog Pilots, Blue Water Grunts: The American Military in the Air, at Sea, and on the Ground, published in 2007 by Random House, reflects his continuing interest in the US Armed Forces.

Kaplan writes that the Indian Ocean has been a center of power for a long time and that the shift to the Atlantic can be seen as an anomaly that will be set straight in future years.

The Revenge of Geography: What the Map Tells Us About Coming Conflicts and the Battle Against Fate (2012) The Book describes how a country's social relations (including government and other institutions) and culture are a product of the geographical characteristic in which they develop.

The Return of Marco Polo's World: War, Strategy, and American Interests in the Twenty-first Century (2018) is a collection of Kaplan's post-2000 essays on the evolving system in Eurasia.

Commissioned by the Pentagon's Office of Net Assessment, the book's lead essay draws parallels between Eurasia's contemporary emergence as a single "battlespace" to its 13th-century geopolitics, when China last constructed a land bridge to Europe.

The book's other essays, published in a range of analytical and journalistic sources, delve into themes such as technology, globalization, and the misguided application of military power.

[19] The essay was written largely in response to Mearsheimer's stance in his controversial 2007 book The Israel Lobby and U.S. Foreign Policy, which was negatively received and described as an anti-Israel polemic by several reviewers.

In the same essay, Kaplan defends the theory of offensive realism Mearsheimer advocates against claims that it entails hawkish or neoconservative foreign policy.

This study and approach, due to its historical associations, is considered a discredited field by academic geographers, but Megoran objects to its influence on Kaplan and on the foreign policy of states.

[1] Istvan Deak, Columbia University Professor Emeritus of History, labels Balkan Ghosts "an often delightful romp through the past and present politics of a region," saying that Kaplan "intends to convince us, and he assuredly does, with gusto, that the peoples of these five alienated countries do indeed form an unhappy whole.

"[28] In his review, Henry R. Cooper, labelled the work a "dreadful mix of unfounded generalizations, misinformation, outdated sources, personal prejudices and bad writing.