Macgregor was the "squadron operations officer who essentially directed the Battle of 73 Easting" during the Gulf War. Facing an Iraqi Republican Guard opponent, U.S. troops with 10 tanks and 13 Bradley fighting vehicles destroyed almost 70 Iraqi armored vehicles with no U.S. casualties in a 23 minute span of the battle. As Macgregor was towards the front of the battle involved in shooting, he didn't "request artillery support or report events to superiors until the battle was virtually over, according to one of his superior officers." The risks he undertook "could have been criticized had the fight turned ugly."

At a November 1993 exercise at the Army's National Training Center at Fort Irwin, Lt. Col. Macgregor's unit vastly outperformed its peers against the "Opposition Force." The series of five battles usually end in four losses and a draw for the visiting units; Macgregor's unit won three, lost one, and drew one. Magregor's unit dispersed widely, took unconventional risks, and anticipated enemy movements.

Macgregor was a top Army thinker on innovation. He "became prominent inside the Army" when he published Breaking the Phalanx, which argued for radical reforms. Breaking the Phalanx was rare in that an active duty military author was challenging the status quo with detailed reform proposals for the reorganization of U.S. Army ground forces. The head of the Army, United States General Dennis Reimer, wanted to reform the Army and effectively endorsed Breaking the Phalanx and passed copies out to generals; however, reforming the army according to the book met resistance from the "board of directors"—the four-star generals—and Reimer did not press the issue.

Many of Macgregor's colleagues thought his unconventional thinking may have harmed his chances for promotion. While an Army NTC official called him "the best war fighter the Army has got," colleagues of Macgregor were concerned that "the Army is showing it prefers generals who are good at bureaucratic gamesmanship to ones who can think innovatively on the battlefield." Macgregor was also seen as blunt, and to some, arrogant. Despite Magregor's top post-Gulf War NTC showing, his Army career was sidelined. The summer of 1997 marked the third time the Army refused to put him under control of a combat brigade, "a virtual death warrant for his Army career, relegating him to staff jobs as a colonel for the remainder of his service."

Macgregor was the top planner for Gen. Wesley Clark, the military commander of NATO, for the attack on Yugoslavia.

In the fall of 2001, Secretary of Defense Donald Rumsfeld, who had read Breaking the Phalanx, insisted that General "Tommy" Franks and his planning staff meet with Colonel Macgregor on 16—17 January 2002 to discuss a concept for intervention in Iraq involving the use of an armored heavy force of roughly 50,000 troops in a no warning attack straight into Baghdad.

Macgregor left the Army in June 2004. He is the vice president of Burke-Macgregor, LLC, a consulting firm based in Reston, Virginia, and he occasionally appears as a guest commentator on television and radio.

Magregor received his Ph.D. from the University of Virginia in international relations.

• Breaking the Phalanx advocated that "the army restructure itself into modularly organized, highly mobile, self-contained, combined arms teams that look extraordinarily like the Marine Corps' Air Ground Task Forces".
• In 2004, Magregor stated that he strongly supported war against Iraq.
• During the beginning of the Iraq War, Macgregor disagreed with those who wanted to slow the advance into Baghdad in order to fight Fedayeen paramilitary forces.
• In 2006, after seven retired generals criticized then Defense Secretary Donald Rumsfeld's handling of the war, Magregor faulted the generals themselves for poor war planning and the resulting complications in Iraq.
• In 2008, Macgregor stated he would argue that American military action in Iraq and Afghanistan "has produced very serious and negative consequences for American national-security interests".
• Macgregor's 2009 book, Warrior's Rage: The Great Tank Battle of 73 Easting, argues that the failure to finish the battle with the Republican Guard in 1991 led to Iraq's second major confrontation with the United States in 2003.
• In 2010, he strongly criticized the counter-insurgency strategy and escalation of troops in Afghanistan.

Publications

Book: Warrior’s Rage: The Great Tank Battle of 73 Easting, Naval Institute Press (September 2009).Article: "Refusing Battle", Armed Forces Journal, (April 2009).Article: “Washington’s War”, Armed Forces Journal, (October 2007).Article: “Fire the Generals!” Defense and the National Interest, (March 2006).Article: XVIII Airborne Corps, Spearhead of Military Transformation, published in Defense Horizon, Center for Technology and Security Policy, National Defense University (2004).Book: Transformation Under Fire: Revolutionizing How America Fights, Praeger Publishing, Inc. (2003)Article: Resurrecting Transformation for the Post-Industrial Age, published in Defense Horizon, Center for Technology and Security Policy, National Defense University (2001).Article: Balkan Limits to Power and Principle, published in Orbis, Vol 45, No. 1 (2001).Article: Transformation and the Illusion of Change, published in National Security Studies Quarterly, Vol. VI, Issue 4 (2000).Article: Joint Operational Architecture: The Key to Transformation, published in Strategic Review, (2000).Article: Transforming Operational Architecture for the Information Age, published by The Jaffee Center, Tel Aviv University, (2001).Article: Command and Control for Joint Strategic Action, published in Joint Force Quarterly (1999).Article: Initiative in Battle Past and Future, published in Marine Corps Gazette (1997)Book: Breaking The Phalanx: A New Design for Landpower in the 21st Century, Praeger Publishing (1997).Article: Setting the Terms of Future Battle for Force XXI, published in Land Warfare Paper, No. 20 (1995).Article: Future Battle: The Merging Levels of War, published in Parameters, Vol. XXII, No. 4 (1992)Article: US and Soviet Military Disengagement From Germany, published in Comparative Strategy, Vol. 8. (1989)Book: The Soviet-East German Military Alliance, Cambridge University Press (1989).Article: The Reliability of Non-Soviet Forces in the Warsaw Pact, Journal of Soviet Studies, University of Glasgow, 1986.