Franklin Roosevelt didn’t want to fight the Vietnam War. He wasn’t, of course, alive when American troops began to trickle into Indochina, and his grasp of the tensions with Soviet Russia that would mature into the Cold War was not fully formed. Indeed, toward the end of World War II, he cut out Winston Churchill so as to confer with Joseph Stalin privately.

But from July 1944 through the early months of 1945, Roosevelt repeatedly set out a clear vision for Vietnam: It should be a trusteeship, governed by the new United Nations, and not a colony, governed by France. “Roosevelt has been more outspoken to me on that subject than any other colonial matter,” Churchill told his foreign secretary, Anthony Eden, “and I imagine it is one of his principal war aims to liberate Indochina from France.”

Then Roosevelt died. His ideas for Vietnam died with him, and before long his successor, Harry S Truman, accepted French possession of Indochina. The rest is (very sad) history, set out in a stunning new book on Dien Bien Phu, the French outpost that collapsed in 1954, by Ted Morgan, whose account of FDR’s abandoned notion has the whiff of tragedy.

FDR’s lost influence on Vietnam

Roosevelt’s death was a turning point in American politics, the conduct of World War II, the character of the presidency, the profile of the Democratic Party and relations among the United States, Great Britain, the Soviet Union and France. All that was known, or could have been surmised, on April 12, 1945, the day he died.

But the implications for Vietnam were not known and could not have been imagined the evening Truman took the presidential oath of office. It is possible to argue that the death warrants of several million Vietnamese and 58,000 Americans, some yet unborn, were signed along with the death certificate of President Roosevelt.

History is full of turning points, some instantly recognizable. Almost everybody understood on the day that Archduke Franz Ferdinand of Austria was assassinated in Sarajevo in 1914 that the world would be different in the years ahead, and that Central Europe would be transformed. So, too, with the German invasion of Poland in 1939 and the Japanese attack on Pearl Harbor 27 months later, both instantly acknowledged as turning points for power politics in Europe and Asia.

But some turning points occur far from view or, if they are prominent events, have unexpected implications. Everyone knows that the election of Barack Obama was an important event. No one knows whether that will inspire a young black person, or someone else, somewhere in America or Africa or somewhere else, to dream big and make history.

Misinterpreted turning points

At the same time, we are surrounded by the effects of turning points that are spectacularly misinterpreted. Who could have imagined that Barry Goldwater’s loss in 1964 would be regarded today as boosting American conservatives’ prospects rather than burying them? (This is received wisdom today, especially since Ronald Reagan’s pre-election speech for Goldwater launched the career that would transform conservatism — and the American political scene.)

Who could have imagined that the Nazis’ use of anti-communist elements of Muslim enclaves to fight the Soviets would have led to the West’s use of the same groups in the Cold War, which in turn would have led to American support of the mujahedeen in Afghanistan in the 1980s, which then would have led to the establishment of an al-Qaida base in Central Asia, which would have led to the terrorist attacks of Sept. 11, 2001? (That is the thesis of Ian Johnson’s new book, “A Mosque in Munich.”)

Teddy’s ties to Pearl Harbor

Then again, who could have imagined that Theodore Roosevelt’s embrace of a Monroe Doctrine for Asia would have encouraged Japan to seek a Greater East Asia Co-Prosperity Sphere that would in turn lead to Pearl Harbor and then to the Cold War? (That is the less-convincing thesis of James Bradley’s “The Imperial Cruise,” published late last year and still selling briskly.)

Perhaps the most intriguing turning points are the ones that go unrecognized for many years. Here’s one: The day in May 1917 when Harry Truman, at age 33, rejoined the Missouri National Guard with the intention of fighting in World War I. That experience gave the 33rd president, the last chief executive without a college degree, the worldly perspective to guide the United States at the end of World War II and the beginning of the Cold War.

Some are apocryphal or hard to prove. For years Americans believed, wrongly, that Fidel Castro had been cut by a professional baseball team, an event that denied him the chance to be a Yankee or a Senator — consider the symbolism of that — and set him on the path to revolution, shaping the destiny of the Kennedy administration, which stumbled at the Bay of Pigs and triumphed during the Cuban Missile Crisis a year later.

Is it possible that Ho Chi Minh’s experience as a messboy on a French ocean liner turned him against his colonial masters, or that his failure to attract support for Vietnamese independence at the Versailles peace conference pushed him toward Moscow, a fateful drift with a significance for Vietnam and the United States at least as important as the death of Roosevelt?

An unnoticed invention

There is, however, one turning point that went unnoticed at the time and whose importance is undeniable today.

In April 1969, Steve Crocker, one year out of UCLA, wrote a “request for comment” that received no attention in a week that included the decision to “Vietnamize” the conflict in Indochina, the cancellation of “The Smothers Brothers Comedy Hour” and the Chicago Eight’s plea of not guilty in a trial involving demonstrations at the Democratic National Convention a year earlier. Crocker’s document included this passage:

“After receiving a message from a HOST, an IMP partitions the message into one or more packets. Packets are not more than 1010 bits long and are the unit of data transmission from IMP to IMP. A 24-bit cyclic checksum is computed by the transmission hardware and is appended to an outgoing packet. The checksum is recomputed by the receiving hardware and is checked against the transmitted checksum. Packets are reassembled into messages at the destination IMP.”

We know this today as the founding document of the Internet.

— David Shribman is executive editor of the Pittsburgh Post-Gazette.