What If?, subtitled The World's Foremost Military Historians Imagine What Might Have Been, is a collection of twenty essays and thirteen sidebars dealing with counterfactual history. It was published by G.P. Putnam's Sons in 1999, ISBN 0-399-14576-1, and this book as well as its two sequels, What If? 2 and What Ifs? of American History, were edited by Robert Cowley. It was later combined with What If? 2 to form The Collected What If?.

Essays

• "Infectious Alternatives" by William H. McNeill
• What if a plague had not forced the Assyrians to withdraw from their siege of Jerusalem in 701 BC?
• "No Glory That Was Greece" by Victor Davis Hanson
• What if the Persians had won the Battle of Salamis?
• "Conquest Denied" by Josiah Ober
• What if Alexander the Great had died at the Battle of the Granicus River?
• "Furor Teutonicus: The Teutoburg Forest, A.D. 9" by Lewis H. Lapham
• What if Varus had defeated Arminius at the Battle of the Teutoburg Forest?
• "The Dark Ages Made Lighter" by Barry S. Strauss
• What if the battles of Adrianople in 378 and Poitiers in 732 had been won by the Romans and the Muslims, respectively?
• "The Death That Saved Europe" by Cecelia Holland
• What if Ogadai Khan had not died in 1242 on the eve of the Mongol siege of Vienna?
• "If Only It Had Not Been Such a Wet Summer" by Theodore K. Rabb
• What if Suleiman the Magnificent had begun his 1529 siege of Vienna earlier in the year?
• "The Immolation of Hernán Cortés" by Ross Hassig
• What if Cortés had been killed or his expedition into Aztec-dominated Mexico had failed?
• "The Repulse of the English Fireships" by Geoffrey Parker
• What if the Spanish Armada had successfully landed in England?
• "Unlikely Victory" by Thomas Fleming
• What if the Americans lost the Revolutionary War? (Thirteen ways are presented here.)
• "What the Fog Wrought" by David McCullough
• What if George Washington and his forces had not escaped after losing the Battle of Long Island?
• "Ruler of the World" by Alistair Horne
• What if Napoleon Bonaparte had chosen to do several things differently?
• "If the Lost Order Hadn't Been Lost" by James M. McPherson
• What if Robert E. Lee had been able to march through Pennsylvania and Maryland without fighting the Battle of Antietam?
• "A Confederate Cannae and Other Scenarios" by Stephen W. Sears
• What if the Civil War had not lasted as long as it did? (Five ways are presented here.)
• "The What Ifs of 1914" by Robert Cowley
• What if Great Britain had remained neutral in World War I? (This and four other possibilities are presented here.)
• "How Hitler Could Have Won The War" by John Keegan
• What if the Wehrmacht had turned toward the Middle East instead of the Soviet Union?
• "Our Midway Disaster" by Theodore F. Cook, Jr.
• What if the Japanese had won the Battle of Midway?
• "D Day Fails" by Stephen E. Ambrose
• What if the Allied invasion of Europe had failed in June 1944?
• "Funeral in Berlin" by David Clay Large
• What if American and not Soviet forces had taken Berlin in 1945?
• "China Without Tears" by Arthur Waldron
• What if the Chinese Civil War had ended with Chiang Kai-shek not marching to retake Manchuria from Mao Zedong and the Communists?