In 2019, Cohen was named the 9th Dean of the Paul H. Nitze School of Advanced International Studies (SAIS) at Johns Hopkins University, succeeding Vali Nasr.
Cohen "is one of the few teachers in the American academy to treat military history as a serious field", according to international law scholar Ruth Wedgwood.
Following this, he taught for four years at the Naval War College in the Department of Strategy, before briefly serving in 1990 on the policy planning staff in the Office of the Secretary of Defense.
In a November 2001 op-ed for The Wall Street Journal, Cohen identified what he called World War IV and advocated the overthrow of Iran's government as a possible next step for the Bush administration.
Cohen claimed "regime change" in Iran could be accomplished with a focus on "pro-Western and anticlerical forces" in the Middle East and suggested that such an action would be "wise, moral and unpopular (among some of our allies)".
"[13] Later in 2001, Cohen, in what was becoming a dominant theme of his writing, advocated war against Iraq once again and proceeded to outline how effortless such a military campaign would be: After Afghanistan, what?
So...[15]In testifying to a congressional House committee later in 2002, Cohen was quoted as saying: ..the choice before the United States is a stark one, either to acquiesce in a situation which permits the regime of Saddam Hussein to restore his economy, acquire weapons of mass destruction and pose a lethal threat to his neighbors and to us, or to take action to overthrow him.
[16]In a piece for the Wall Street Journal on 6 February 2003, Cohen fervently praised the presentation given by then Secretary of State Colin Powell in which he outlined the case for military action against Iraq to the United Nations.
What the father in me expects from our leaders is, simply, the truth—an end to happy talk and denials of error, and a seriousness equal to that of the men and women our country sends into the fight.
[18]As a member of the Defense Policy Board Advisory Committee Cohen had also been engaged in meetings involving US President George Bush.
Cohen found unsupported the opinion that, compared to civilians, veterans possess "sheer moral authority" or "are uniquely qualified to make judgments on matters of war and peace."
An article by Ximena Ortiz in the National Interest called Cohen's ability to do the job into question and attempted to juxtapose his previous statements on the Bush administration foreign policy with the resulting war in Iraq.
[22]As the controversy played out in the media, a rebuttal of sorts from Ruth Wedgwood, international law scholar at Johns Hopkins University, sought to defend Cohen from criticism.
In it, he maintains that "Putin is indeed a brutal Great Russian nationalist who understands that Russia without a belt of subservient client states is not merely a very weak power but also vulnerable to the kind of upheaval that toppled Yanukovych’s corrupt and oppressive regime."
He mentions The New York Times publication of the op-ed by Putin on the Syrian chemical arms question and links to the text of the NATO accord as a token of good faith.
[28] Cohen wrote an op-ed piece in The Washington Post on 15 November 2016 after the 2016 presidential election affirming his stance against the presidency of Donald Trump.
In the piece he states: I am a national security Never-Trumper who, after the election, made the case that young conservatives should volunteer to serve in the new administration, warily, their undated letters of resignation ready.
And friends who urged us to tone it down, to make our peace with him, to stop saying as loudly as we could "this is abnormal," to accommodate him, to show loyalty to the Republican Party, to think that he and his advisers could be tamed, were wrong.