|1973 : U.S. withdraws from Vietnam |
Two months after the signing of the Vietnam peace agreement, the last U.S. combat troops leave South Vietnam as Hanoi frees the remaining American prisoners of war held in North Vietnam. America's direct eight-year intervention in the Vietnam War was at an end. In Saigon, some 7,000 U.S. Department of Defense civilian employees remained behind to aid South Vietnam in conducting what looked to be a fierce and ongoing war with communist North Vietnam.
In 1961, after two decades of indirect military aid, U.S. President John F. Kennedy sent the first large force of U.S. military personnel to Vietnam to bolster the ineffectual autocratic regime of South Vietnam against the communist North. Three years later, with the South Vietnamese government crumbling, President Lyndon B. Johnson ordered limited bombing raids on North Vietnam, and Congress authorized the use of U.S. troops. By 1965, North Vietnamese offensives left President Johnson with two choices: escalate U.S. involvement or withdraw. Johnson ordered the former, and troop levels soon jumped to more than 300,000 as U.S. air forces commenced the largest bombing campaign in history.
During the next few years, the extended length of the war, the high number of U.S. casualties, and the exposure of U.S. involvement in war crimes, such as the massacre at My Lai, helped turn many in the United States against the Vietnam War. The communists' Tet Offensive of 1968 crushed U.S. hopes of an imminent end to the conflict and galvanized U.S. opposition to the war. In response, Johnson announced in March 1968 that he would not seek reelection, citing what he perceived to be his responsibility in creating a perilous national division over Vietnam. He also authorized the beginning of peace talks.
In the spring of 1969, as protests against the war escalated in the United States, U.S. troop strength in the war-torn country reached its peak at nearly 550,000 men. Richard Nixon, the new U.S. president, began U.S. troop withdrawal and "Vietnamization" of the war effort that year, but he intensified bombing. Large U.S. troop withdrawals continued in the early 1970s as President Nixon expanded air and ground operations into Cambodia and Laos in attempts to block enemy supply routes along Vietnam's borders. This expansion of the war, which accomplished few positive results, led to new waves of protests in the United States and elsewhere.
Finally, in January 1973, representatives of the United States, North and South Vietnam, and the Vietcong signed a peace agreement in Paris, ending the direct U.S. military involvement in the Vietnam War. Its key provisions included a cease-fire throughout Vietnam, the withdrawal of U.S. forces, the release of prisoners of war, and the reunification of North and South Vietnam through peaceful means. The South Vietnamese government was to remain in place until new elections were held, and North Vietnamese forces in the South were not to advance further nor be reinforced.
In reality, however, the agreement was little more than a face-saving gesture by the U.S. government. Even before the last American troops departed on March 29, the communists violated the cease-fire, and by early 1974 full-scale war had resumed. At the end of 1974, South Vietnamese authorities reported that 80,000 of their soldiers and civilians had been killed in fighting during the year, making it the most costly of the Vietnam War.
On April 30, 1975, the last few Americans still in South Vietnam were airlifted out of the country as Saigon fell to communist forces. North Vietnamese Colonel Bui Tin, accepting the surrender of South Vietnam later in the day, remarked, "You have nothing to fear; between Vietnamese there are no victors and no vanquished. Only the Americans have been defeated." The Vietnam War was the longest and most unpopular foreign war in U.S. history and cost 58,000 American lives. As many as two million Vietnamese soldiers and civilians were killed.
1973 : U.S. withdraws from Vietnam
1879 : British victory at Kambula
1974 : Mariner 10 visits Mercury
1776 : Putnam named commander of New York troops
1979 : Nuclear accident at Three Mile Island
At 4 a.m. on March 28, 1979, the worst accident in the history of the U.S. nuclear power industry begins when a pressure valve in the Unit-2 reactor at Three Mile Island fails to close. Cooling water, contaminated with radiation, drained from the open valve into adjoining buildings, and the core began to dangerously overheat.
The Three Mile Island nuclear power plant was built in 1974 on a sandbar on Pennsylvania's Susquehanna River, just 10 miles downstream from the state capitol in Harrisburg. In 1978, a second state-of-the-art reactor began operating on Three Mile Island, which was lauded for generating affordable and reliable energy in a time of energy crises.
After the cooling water began to drain out of the broken pressure valve on the morning of March 28, 1979, emergency cooling pumps automatically went into operation. Left alone, these safety devices would have prevented the development of a larger crisis. However, human operators in the control room misread confusing and contradictory readings and shut off the emergency water system. The reactor was also shut down, but residual heat from the fission process was still being released. By early morning, the core had heated to over 4,000 degrees, just 1,000 degrees short of meltdown. In the meltdown scenario, the core melts, and deadly radiation drifts across the countryside, fatally sickening a potentially great number of people.
As the plant operators struggled to understand what had happened, the contaminated water was releasing radioactive gases throughout the plant. The radiation levels, though not immediately life-threatening, were dangerous, and the core cooked further as the contaminated water was contained and precautions were taken to protect the operators. Shortly after 8 a.m., word of the accident leaked to the outside world. The plant's parent company, Metropolitan Edison, downplayed the crisis and claimed that no radiation had been detected off plant grounds, but the same day inspectors detected slightly increased levels of radiation nearby as a result of the contaminated water leak. Pennsylvania Governor Dick Thornburgh considered calling an evacuation.
Finally, at about 8 p.m., plant operators realized they needed to get water moving through the core again and restarted the pumps. The temperature began to drop, and pressure in the reactor was reduced. The reactor had come within less than an hour of a complete meltdown. More than half the core was destroyed or molten, but it had not broken its protective shell, and no radiation was escaping. The crisis was apparently over.
Two days later, however, on March 30, a bubble of highly flammable hydrogen gas was discovered within the reactor building. The bubble of gas was created two days before when exposed core materials reacted with super-heated steam. On March 28, some of this gas had exploded, releasing a small amount of radiation into the atmosphere. At that time, plant operators had not registered the explosion, which sounded like a ventilation door closing. After the radiation leak was discovered on March 30, residents were advised to stay indoors. Experts were uncertain if the hydrogen bubble would create further meltdown or possibly a giant explosion, and as a precaution Governor Thornburgh advised "pregnant women and pre-school age children to leave the area within a five-mile radius of the Three Mile Island facility until further notice." This led to the panic the governor had hoped to avoid; within days, more than 100,000 people had fled surrounding towns.
On April 1, President Jimmy Carter arrived at Three Mile Island to inspect the plant. Carter, a trained nuclear engineer, had helped dismantle a damaged Canadian nuclear reactor while serving in the U.S. Navy. His visit achieved its aim of calming local residents and the nation. That afternoon, experts agreed that the hydrogen bubble was not in danger of exploding. Slowly, the hydrogen was bled from the system as the reactor cooled.
At the height of the crisis, plant workers were exposed to unhealthy levels of radiation, but no one outside Three Mile Island had their health adversely affected by the accident. Nonetheless, the incident greatly eroded the public's faith in nuclear power. The unharmed Unit-1 reactor at Three Mile Island, which was shut down during the crisis, did not resume operation until 1985. Cleanup continued on Unit-2 until 1990, but it was too damaged to be rendered usable again. In the more than two decades since the accident at Three Mile Island, not a single new nuclear power plant has been ordered in the United States.
1979 : Nuclear accident at Three Mile Island
1939 : Spanish Civil War ends
1969 : Eisenhower dies
1774 : British Parliament adopts the Coercive Acts