If, as the United States believed, the South Vietnamese were capable of dealing with the Vietcong and regular NVA troops located in the South at the time of the signing, why then did the Paris Agreements fail? Was the reason for failure, as some writers such as Frank Snepp claim, due to the fact that the United States was only negotiating to allow for a "decent interval" to transpire before the final collapse and allow the U.S. to gracefully bow out of Southeast Asia? In the end, this is what basically occurred. However, it is doubtful that the final tragic outcome in South Vietnam was ever consciously considered by the men involved in the negotiations at the time.

A key point to consider in answering these complicated questions is that the equilibrium of forces present in January 1973 did not remain stationary in the following years leading to April 30, 1975. In the period 1973 to 1975, when Soviet military aid to North Vietnam quadrupled, American military aid to South Vietnam was cut from over $2.5 billion in fiscal year 1973 to $700 million is fiscal year 1975.27 This tremendous cutback in aid to South Vietnam after the signing of the Paris Agreements, while infiltration of troops and supplies by North Vietnam into the South increased, seriously affected the equilibrium of forces that had been achieved in 1973; it definitely shifted the balance of power to the North Vietnamese by 1975. Led by Senator J. William Fulbright, the U.S. Congress passed, in June 1973, a bill to cutoff funds for combat activities in South east Asia. It set August 15, 1973 as the date for termination of U.S. bombing in Cambodia, and required Congressional approval for funding of U.S. military action in any part of Indochina. This action by Congress had such an impact on President Nixon at the time that he wrote to House Speaker Carl Albert and U.S. Senate Majority Leader Mike Mansfield to voice his grave concern about the serious consequences that would result:

The abandonment of a friend will have a profound impact in other countries, such as Thailand, which have relied on the constancy and determination of the United States, and I want the Congress to be fully aware of the consequences of its action....

... I can only hope that the North Vietnamese will not draw the erroneous conclusion from this Congressional action that they are free to launch a military offensive in other areas of Indochina. North Vietnam would be making a very dangerous error if it mistook the cessation of bombing in Cambodia for an invitation to fresh aggression or further violations of the Paris agreements. The American people would respond to such aggression with appropriate action.28

In his memoirs, President Nixon later confessed that Congress had removed the possibility of military action and he only had words with which to threaten North Vietnam. Unfortunately, the North Vietnamese knew this. The Nixon Administration was well aware of North Vietnam's intentions, but the President's power to act in order to carry out the promises made to South Vietnam was seriously hampered by an increasingly hostile Congress and the final unraveling of Presidential authority by the events surrounding Watergate. Henry Kissinger eloquently expresses his thoughts on the goal the United States attempted to achieve in Paris and a reason for failure:

We had no illusions about Hanoi's long-term goals. Nor did we go through the agony of four years of war and searing negotiations simply to achieve a "decent interval" for our withdrawal. We were determined to do our utmost to enable Saigon to grow in security and prosperity so that it could prevail in any political struggle. We sought not an interval before collapse, but lasting peace with honor. But for the collapse of executive authority as a result of Watergate, I believe we would have succeeded.29

So, it was that an agreement negotiated in good faith by the executive branch of our government was undone by the Congress and public that had grown weary of their commitment to a burdensome ally and wanted out of Vietnam completely. While it is certainly true that the South Vietnamese leadership must bear the ultimate responsibility for the final tragic outcome of the war, the United States must also bear some responsibility for refusing to fulfill its obligations to South Vietnam during the two year period following the signing of the Paris agreements.