Somebody once said that Communism is the longest and most expensive route from capitalism to capitalism, and certainly Vietnam today validates that glib observation.  After 24 years of market-oriented reforms that expanded wealth each year, the nation that once convulsed a superpower now records GDP growth of 6.2%.  "This is not a communist country," says Le Cong Dinh, a lawyer and government critic, still under house arrest.  "They try to continue the ideology.  But what we see on the streets of Vietnam is capitalism, not communism," he told AFP.

This result, coming after the death of millions of Vietnamese, 58,000 American troops, and half a million "boat people" fleeing the Communist government, and the execution and imprisonment of tens of thousands in re-education camps, leads a moral critic to revulsion at the sheer waste of human life that was the Vietnam War.

A victory for the North was not inevitable.  The American and European left, sympathetic to the cause of North Vietnam, glossed over Communist atrocities and claimed that the South Vietnamese nation was doomed from the beginning as an American construct, with no public legitimacy and irremediable corruption.

But an important new book, Black April, by George Veith, argues instead that after the American withdrawal of all combat troops from Vietnam in 1973, South Vietnam fought surprisingly well at almost every turn, and the Communist invasions were initially stymied by sheer valor.

Beginning with the Easter Offensive of 1972 and throughout the next two years, North Vietnam tried and failed to defeat the South in large-scale invasions that openly breached the Paris Peace Accords of January 1973.  These violations garnered no attention from a war-weary American public.  Congress, against the advice of the Nixon and Ford administrations, cut off nearly all aid to the South in an amazingly brazen betrayal of its ally, and prohibited any U.S. military action across the whole of Indochina. 

With no spare parts or fuel resupply, still the free South fought on.  At Xuan Loc, a single ARVN division crushed a Communist force three times its size.  In March and April 1975, the South won multiple large clashes, from Mo Tau in the north to Ben Cau in the central highlands to Can Tho and Long An in the south.

But by March, the South Vietnamese air force was almost completely grounded from the wear and tear of endless combat sorties with no resupply from its former ally.  It could neither move troops to defend a nearly 1,000 mile flank in the west nor conduct close air support against NVA attacks on the cities.

The resulting attacks on civilian populations by the Communist side created, surprisingly, a huge boon for the North.  Its sheer evil reputation for mass killing of civilians caused hundreds of thousands of terrified men, women, and children to flee from the sites of battle as refugees.  This blocked almost every road the ARVN tried to use in moving its troops from one breach in the line to another.  In April, when the ARVN tried to form up a defensive perimeter around Da Nang, 500,000 panicked civilians clogged the roads to get into the city.  In the last stand for Saigon, only one seventh of the entire army was available, because the rest of the troops could not be moved.  The North's reputation for terrorism paid off in spades.

As NATO's troops draw down in Afghanistan today, we should well fear the consequences of leaving behind an under-supplied ally.  Will Kabul in April 2016 look like Saigon in April 1975?

Christopher S. Carson is a lawyer in private practice and holds a master's in national security studies from Georgetown University.