This phrase, once a statement of optimism, has become so inextricably linked with the United States' disastrous involvement in Vietnam, that it is almost always a statement of irony. The phrase has been so frequently used in reference to that ultimate in screwed pooches, in fact, that it has become a cliché.

The events, theories, opinions, ramblings and recriminations about the Vietnam War are material for dozens, if not hundreds of other nodes, but perhaps we should describe how this phrase came to mean its exact opposite.

In late 1967, General Earle G. Wheeler, Chairman of the Joint Chiefs of Staff, urged General William C. Westmoreland, the commander of US forces in Vietnam, to release optimistic estimates of the United States' military position in Vietnam.  The North Vietnamese Army and Viet Cong were portrayed to the press as being on the ropes.

Then, in December, after these estimates came out, National Security Adviser Walter W. Rostow said

"I see light at the end of the tunnel."
in a televised speech, despite the fact that the White House knew that the Viet Cong were preparing a major offensive.  Sure enough, the Tet Offensive was soon launched, showing that the war would not be over for a long, long time.

The Tet offensive shook American public opinion about the Vietnam War.  The American press, and the American public came away feeling that they had been lied to, and Rostow's 'light at the end of the tunnel' speech was the primary symbol of this.

The irony of this phrase caught on immediately.  In February, 1968, humorist Art Buchwald released a column about General Custer sending back a dispatch about there being a 'light at the end of the tunnel' in his campaign against the Sioux...just before the Little Big Horn.

Curiously, extracts of President Lyndon Baines Johnson's secret tapes from this time contain the statement

"Light at the end of the tunnel? We don't even have a tunnel; we don't even know where the tunnel is."
indicating that Johnson may not have agreed with Rostow's assessment.  Although we must remember that Johnson knew the tapes were being made, the statement may have been political grandstanding on Rostow's account, or an attempt to force Johnson into making a decision by putting words into his mouth.

Legend tells us that during the humiliating 1975 end of the entire Vietnam fiasco, the graffito

Will the last person out of the tunnel please turn out the light?

appeared on Hanoi walls. A different source said that "Would the last Marine to leave Vietnam please turn out the light at the end of the tunnel? appeared on a Da Nang outhouse.

Today, 'light at the end of the tunnel' is used by political reporters and talking heads with nauseating frequency, meaning variously:

The phrase
"The light at the end of the tunnel is just the light of an oncoming train."
has been attributed to both poet Robert Lowell and his wife, Lady Caroline Blackwood.

Wunderhorn1 has pointed out an excellent variation on this, made by Iraqi Deputy Prime Minister Tareq Aziz, after having this cliché thrown at him during a CNN interview...

"Nobody has shown us a light at the end of the tunnel. There is a tunnel after the tunnel."

One would have thought Christiane Amanpour had more sense than to ask something so banal.