On Pearl Harbor Day, historians continue to debate the mysteries of Pearl Harbor. The Japanese attack created some of the great unanswered questions of military history.

By Peter Grier, Staff writer / December 7, 2011

In this Dec. 7, 1941 file photo, a small boat rescues a crew member from the water as heavy smoke rolls out of the stricken USS West Virginia after the Japanese bombing of Pearl Harbor, Hawaii.

AP/File

WASHINGTON

Pearl Harbor. In the United States, the name alone means surprise, defeat, and the rise of common purpose from ashes. Seventy years on, the Japanese surprise attack on US forces assembled in Hawaii remains one of the American people’s most powerful historic memories.

Every year on Dec. 7 the nation pauses to remember the 2,400 US personnel who died that day, and the generation of ordinary citizens which picked up Pearl Harbor’s fallen flag and fought to victory in World War II.
“We look to December 7, 1941, to draw strength set by the example of these patriots and to honor all who have sacrificed for our freedom,” said President Obama in his proclamation for Pearl Harbor Remembrance Day 2011.

RECOMMENDED: Pearl Harbor: 5 top books on the attack

But seven decades later, Pearl Harbor also remains a mystery. More specifically, it remains an event that has produced some of the great unanswered questions of military history.
Why did the Japanese attack a nation whose industrial might was an order of magnitude larger? Why didn’t the US see the signs that a strike was coming? Who in the US chain of command was most responsible for American unpreparedness?
Today, historians continue to debate many of Pearl Harbor’s puzzles, producing new evidence and theories. Here are just a few of those continued conundrums.

Why weren't US bases on alert?

The first wave of Japanese aircraft hit Pearl Harbor at about 8 a.m. local time on Dec. 7, 1941. Within hours, Japanese forces also struck the Philippines, Wake Island, Guam, and other Pacific targets. US units everywhere were taken by surprise.
“The nakedness of America’s Pacific bases continues to puzzle posterity,” writes British journalist and historian Max Hastings in his gripping new history of World War II, “Inferno.”
Mr. Hastings dismisses claims that President Franklin Roosevelt allowed Pearl Harbor to be attacked to draw the US into war. But he says it is nonetheless “extraordinary” that the US political and military leadership did not ensure that Pearl Harbor and other Pacific bases were on full precautionary footing.
The late Gordon Prange, a University of Maryland professor who was perhaps America’s foremost authority on the attack, believed that the core problem was that the US government did not in its heart believe that its own warnings about imminent Japanese aggression were true.
“This fundamental disbelief is the root of the whole tragedy,” concluded Mr. Prange in his book, “At Dawn We Slept.”

A congressional committee conducted extensive hearings into the Pearl Harbor disaster after the war ended. Among its conclusions were that Army forces were so focused on training they lost sight of possible attack – and that Army commanders were so worried about sabotage they locked up anti-aircraft ammunition rather than distribute it to gun sites. The Navy did not maintain aircraft patrols at sea due to lack of equipment – but neither did commanders order a picket line of surface ships instead.
In the current issue of Naval History, a journal of the US Naval Institute, historians Jonathan Parshall and J. Michael Wenger argue that an overlooked answer to the question of why the US was surprised is that US commanders did not understand how quickly aircraft carrier warfare was evolving.
The Pearl Harbor strike plan involved the melding of planes from many carriers into a hornet swarm of attackers. That was a skill the US did not know the Japanese military possessed.

“The US Navy had no real inkling of Japanese carrier warfare capabilities and therefore could not accurately assess likely operational targets,” write Messrs. Parshall and Wenger.

Why didn't the Japanese press their advantage?

After two waves of aircraft devastated Pearl Harbor’s Battleship Row and US air bases, Japanese pilots returned to their carriers in triumph. Adm. Chuichi Nagumo then led a discussion on whether another attack was feasible. Many air commanders supported such a follow-up, believing that fuel dumps, repair shops, and other US logistical sites were now vulnerable.
A cautious commander, Nagumo decided against more action. It would have required reloading aircraft on deck at sea at a time when the location of US carriers and submarines was unknown. Japanese forces had already won a spectacular victory. Why waste that gain?
“Nagumo’s decision to turn back came as a disappointment to many of his airmen, who wanted to exploit their opportunity,” wrote Prange.
Destruction of Pearl Harbor’s infrastructure might have forced the US to withdraw its naval forces to the US West Coast. For decades, some historians have argued that Nagumo missed an opportunity that maybe, just maybe, could have turned the course of the war.
However in his book, “Inferno,” Max Hastings argues that new research shows a follow-on attack was not feasible.
“The winter day was too short to launch and recover [another wave of aircraft], and in any event Japanese bomb loads were too small to plausibly wreck Pearl’s repair bases,” Mr. Hastings writes.

What would have happened if the US had lost?

How would the world have been different if US forces had been on alert that Sunday morning in December? After all, it would have taken only a few hours' early warning to perhaps reverse the battle’s decision. US fighters would have been aloft and anti-aircraft batteries alerted. They could have taken a large toll on Japan’s incoming planes.

Today’s conventional wisdom is that Japan, in winning the battle, lost the war. Many of the ships destroyed at Pearl were refloated and rebuilt for later fights. Most important, a US public that had been divided over entry into the war became united at a stroke.
“No more did Americans ask whose fight it was or question what they should do about it,” wrote Prange.
As Prange also notes, it is likely that the US would have entered World War II at some point even if Pearl Harbor never happened. Whether US civilians would have universally supported such a move in the absence of a surprise attack is a great historical unknown.
As to what might have happened if the Pacific Fleet had repulsed its attackers, it’s quite possible that the fleet’s commander, Adm. Husband E. Kimmel, would have launched his battleships and carriers out on a mission to catch and destroy the Japanese, writes Ohio State University military historian Mark Grimsley.
Kimmel was an offensive-minded commander who dreamed of replicating the victories of the great British admirals of the past. Within several weeks he could have gathered US naval power near Wake Island for a possibly decisive encounter.

Both sides would have had eight battleships available for a fight, writes Mr. Grimsley. The Japanese would have had a slight edge in aircraft carriers, but the US would have benefited from land-based planes from Wake Island bases.
The outcome would have been impossible to predict. A US victory could have greatly shortened the Pacific War. But “a decisive American defeat would have been far worse than the historical Pearl Harbor attack,” writes Grimsely. “Most of the vessels damaged or sunk [at Pearl] were subsequently repaired and returned to action, whereas any warships lost in the Central Pacific would have disappeared beneath thousands of feet of water,” writes Grimsley on Military History magazine’s website.