Retrospectives on the atomic bombings of Hiroshima and Nagasaki conjure up Theodore Roosevelt for me. That goes double when the anniversary is a multiple of ten—as it is today, the seventieth anniversary of Enola Gay’s strike on Hiroshima. Commentators work themselves into high moral dudgeon when that terminal zero recurs. But preening constitutes a poor substitute for dispassionate learning from contemporary or past decisionmakers. In 1910 former president Roosevelt told an audience at the Sorbonne:

“It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood....”

One imagines TR would have even tarter words for critics writing decades after the fact. It’s easy to pass judgment with the advantage of hindsight. Think about it. Scholars typically know far more about what was happening than did historical figures making the decisions. The fog of war has cleared. Passions have evanesced. Archives have been compiled, organized, and opened for leisurely research. And scholars know what took place afterward. They can trace cause-and-effect, using data not available to the protagonists to evaluate the results of their decisions.

Experts’ verdicts, consequently, are commonly short on empathy for protagonists in world-historical affairs—protagonists like President Harry S. Truman and his lieutenants in 1945, contemplating how to put a definite end to the Pacific War at least cost to the Allies. That’s a shame: all too often, strategy is the art of choosing the least awful course of action—and doing so at times of extreme stress, rampant uncertainty, and narrowing options. The climate surrounding decision-making warrants a measure of generosity toward historical figures.

And indeed, the strategic canon cautions against retrospective sagacity. Military theorist extraordinaire Carl von Clausewitz, for one, acknowledges the hazards before decisionmakers—and urges students of military history not to render too-facile judgments on their forebears. In today’s parlance, he reprimands Monday-morning quarterbacks. Posterity, insists Clausewitz, must not “condemn a method without being able to suggest a better alternative.”

To do their intellectual work evenhandedly, analysts should undertake “critical analysis.” That means appraising past deeds using information available to commanders or officials at the time—and no more. This is elementary fairness, not to mention sound methodology. “If the critic wishes to distribute praise or blame,” continues Clausewitz, he must “put himself exactly in the position of the commander; in other words, he must assemble everything the commander knew and all the motives that affected his decision, and ignore all that he could not or did not know, especially the outcome.”

Only then is a just ruling possible. And only then can posterity learn the lessons of past successes and failures, and harness that insight to improve future decisionmaking. Which brings us back to Hiroshima. What did U.S. political and military leaders know about atomic weapons in the summer of 1945, when they were debating the endgame against imperial Japan? Did they fully grasp the import of such attacks?

Well, they certainly knew a game-changing weapon had been fielded. Mass destruction had long been possible in human conflict—witness the world wars—but the atomic bomb compressed mass destruction into an instant. Blast, heat, shock: these were familiar things. All explosives generated them, if on a infinitesimal scale by comparison. But what about the nuclear effects from a detonation? These were new, and unfamiliar.

Indeed, scientists, engineers, and warfighters were still experimenting with nuclear weapons in the mid-1950s, trying to learn their ins and outs. Experimentation involves trial and error. In Operation Castle (1954), for instance, a test thermonuclear warhead produced over twice the yield expected—and created serious diplomatic troubles for Washington when the Japanese fishing vessel Lucky Dragon No. 5 was irradiated. Lucky Dragon’s master perished afterward—helping give rise to the Japanese anti-nuclear movement and creating headaches for the U.S.-Japan alliance for decades.

Truman & Co. could hardly have known in 1945 what the scientific-technical community was still sorting out a decade hence. As Clausewitz might counsel, it’s crucial not to evaluate their actions by what we know from Cold War history, with its nuclear tests, its near-misses like the Cuban Missile Crisis, and a nuclear arms race of gobsmacking proportions. Fault the U.S. leadership if you must—but factoring in immutable limits on knowledge and foresight should temper judgment.

What about strategic alternatives? The president could have abjured using the new device, simply because it was so new and untried. Or, toy around with counterfactuals. What would America have done had the Manhattan Project stalled out or been delayed for a few years, foreclosing the atomic option until long after U.S. naval forces reached the Japanese home islands?

To oversimplify a trifle, U.S. forces had direct and indirect alternatives in 1945. Barring the atomic option, they could have invaded the home islands or cordoned them off, interdicted shipping, and pounded away from sea and sky.

Another dose of strategic theory is in order here. One of my forebears in Newport, Admiral J. C. Wylie, subdivides strategy into “sequential” and “cumulative” strategies. Sequential strategies are easy to grasp. They’re linear. Sequential campaigns unfurl from point A to B to C. Each action depends on the last while determining the next. You can plot them on a map or nautical chart using lines, curves, and vectors. To stick with Pacific War examples, Nimitz’s and MacArthur’s westward offensives were sequential in nature.

Invading the home islands was the sequential option for Truman and his commanders. And indeed, the armed forces drew up invasion plans starting with Operation Olympic, set for Kyushu in October 1945. The president shied away from setting amphibious landings in motion, however, estimating that American losses would be fearful to behold and popular opinion at home might plummet. The atomic bombings were preferable. But if the bomb hadn’t been ready, Truman could have proceeded on the logic that the direct approach was the decisive approach: throw down the enemy, plant your boot on his neck, and dictate terms.

But again, this alternative was unpalatable in the extreme for Truman. Military planners extrapolated from past amphibious offensives—in particular on Okinawa, still fresh in memory—and estimated that a vast bloodletting would ensue should U.S. troops land on Kyushu and elsewhere. If seizing Okinawa was hard, conquering the far bigger, more populous home islands would have proved daunting indeed. Americans back home may not have put up with such loss of life after four years of hard fighting overseas and economic sacrifice at home.

What was Washington’s cumulative option? Wylie is much taken with this approach. Cumulative campaigns are nonlinear. They’re made up of tactical actions scattered across the map, none of which depends on the others for the effects it creates. Each action is largely inconsequential in itself. Seeing a merchant ship torpedoed is a bad thing, for instance, but it’s hardly a backbreaker for any serious combatant. In aggregate, though, minor blows can wear down or dishearten an opponent.

To proceed in a nonlinear manner, U.S. forces could have gone back to their prewar playbook and executed War Plan Orange. War Plan Orange envisioned prosecuting an offensive naval war “directed toward the isolation and exhaustion” of Japan “through control of her vital sea communications and through offensive operations against her armed forces and her economic life.” A simple concept: surround and strangle the enemy homeland from the sea.

This would have constituted an extension of longstanding strategy. U.S. Pacific Fleet submarines had commenced raiding Japanese shipping while the battle fleet was still afire at Pearl Harbor. As U.S. naval operations progressed across the Pacific, sub tenders and foreign bases moved the boats closer and closer to their patrol grounds. By 1945, having sunk most of the Imperial Japanese Navy and merchant fleet, U.S. Navy submarine and surface forces could have encircled the home islands, cutting them off from the rest of the empire and its all-important natural resources; pummeled the islands repeatedly with naval gunfire and sea- and land-based aircraft; and in effect starved Japan into submission.

Indeed, American fleet boats had already done most of the work by 1945. Submarine warfare had dispatched 1,113 merchantmen—oilers, freighters, and transports of various types. Losses outnumbered shipbuilding rates by a factor of four to one. With few hulls left to carry bulk commodities, imports such as oil, coal, and iron had fallen by 90 percent. Exhausting Japan from the sea would’ve kept the casualty count down for U.S. Army and Marine forces, easing Truman’s political problems at home. Bottom line, a maritime blockade could have proved strategically decisive against this resource-poor island state.

Heavy costs to the enemy, relatively light costs to friendly forces: a blockade had much to recommend it. The chief drawback to cumulative campaigns is that this approach is protracted and agonizing. It may have taken months, or even years, to compel Tokyo to capitulate. Prosecuting a blockade would have forced the United States to stay on a war footing against Japan during the early stages of the Cold War. And, in the end, Americans would have been denied the decisive victory sealed on the decks of the battleship Missouri.