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KYIV, UKRAINE – FEBRUARY 20: In this handout photo issued by the Ukrainian Presidential Press Office, U.S. President Joe Biden meets with Ukrainian President Volodymyr Zelensky at the Ukrainian presidential palace on February 20, 2023 in Kyiv, Ukraine. The US President made his first visit to Kyiv since Russia’s large-scale invasion last February 24. (Photo by Ukrainian Presidential Press Office via Getty Images)Ukrainian Presidential Press Office via Getty Images

History has a way of reprising itself in parallel, if not precise leitmotifs — why else would we study it? 

The travesty of Kabul airport in 2021, a botched U.S. withdrawal that almost certainly emboldened Vladimir Putin and encouraged his invasion of Ukraine, is a modern reflection of the 1975 Saigon evacuation. Both indicated a decline in American power and the absence of American resolve. In both cases, the strategic arguments in favor of engagement, of manning the distant rampart, were ignored or lampooned. 

Yet, history is not cyclical. In Ukraine, the United States has a chance to demonstrate its strategic resolve, to avoid the failure of Vietnam and, in turn, prevent a Eurasian strategic confrontation with nuclear implications.

American military involvement in Vietnam — the 50th anniversary of its end being marked May 11-13 in Washington — had well-cataloged missteps. But the underlying strategic logic of the U.S. engagement from 1945 onward was sound. Situated on the eastern edge of the Indochinese Peninsula, Vietnam’s location and robust ports at Haiphong and Da Nang made the onetime French colony a geopolitical prize. Particularly once Mao Zedong’s communists took control of mainland China, Vietnam became a critical rampart for the American-led Eurasian anti-communist coalition. This logic only intensified with time.

The Chinese Communist Party, until the 1960s under Soviet control, pushed outward rapidly. In May 1950, it took Hainan Island, Taiwan’s major southern bastion; that June, the Korean Communists — many of whom had fought alongside the Chinese Communists against Japan — mounted a lightning invasion of the peninsula’s south. China intervened months into the war, leading to a protracted superpower struggle darkened by nuclear shadows. A year after the Korean armistice, China again attacked Taiwan, capturing several outlying islands.

The so-called Domino Theory has gained a poor reputation in the United States, partly for good reason. As articulated in the American public education system, the Domino Theory stems from an irrational fear of communist ideology, with the countries that border communist powers somehow falling prey to the mystical machinations of Marxism. But the thesis, if properly defined, contains several truths.

The communist bloc was expansionist, seeking to gain mastery of Eurasia and to reorganize it along communist lines. The more territory that communist powers held, the more resources they could access, and the more pressure points they could cultivate against other countries. A domino effect was by no means inevitable — America and its allies could resist communist aggression in specific areas, while more limited engagements in other regions might suffice — but the communist powers were accruing specific strategic gains to be marshaled in a general war against the West. Thus, Vietnam was a strategic gem in an iron crown.

Unfortunately, that rational American strategy was not the specific logic of the Kennedy or Johnson administrations, to their detriment. Indeed, a clear articulation of Vietnam’s role in Eurasian competition may have prompted a variety of different military decisions before 1968. 

Far more military pressure could have been applied against North Vietnam than was brought to bear; the United States could have mounted offensive operations past the poorly-named Demilitarized Zone (DMZ), at minimum to dislodge the North’s artillery and supply depots. Indeed, pressure against Cambodia and Laos to disrupt the Ho Chi Minh Trail also undermined communist supplies and cohesion. Much like in Afghanistan decades later, the key to the war lay beyond the immediate territory of combat.

The year 1968 became a break point because of the Tet Offensive — a strategic disaster for the North Vietnamese Army and Viet Cong insurgency but a political triumph for them following the American media’s coverage of it. It destroyed the Viet Cong as a fighting force, while the North’s army could not mount another offensive until 1972. 

Even during this period of weakness, the United States restrained itself, partly for domestic political reasons, partly because it believed China would intervene if the U.S. pushed into the North, and partly from fear of nuclear escalation. Chinese forces were in Vietnam but there was no indication that they would have supported the North in a major military engagement, particularly as the Soviets and Chinese began jockeying for power in Southeast Asia.

Ironically, even after the U.S. made its fateful choice to reduce its involvement in Vietnam for overwhelmingly domestic political reasons, the United States still could have held the line. Despite a greatly reduced commitment, it assisted South Vietnam’s army against a ferocious northern offensive in 1972, with few American losses. The U.S.-enabled South Vietnamese units fought remarkably well once they gained a grasp of the strategic situation and their command was reshuffled.

Moreover, the U.S. was eminently capable of waging multiple proxy wars concurrently while maintaining the balance in Europe: American supplies sustained the Israel Defense Forces during their 1973 war with a Soviet-backed Arab coalition, which ultimately allowed the U.S. to unravel the Soviet position in the Middle East; American intelligence also maintained an effective presence in Latin America — and, all the while, the U.S. held the line in Central Europe alongside its NATO allies.

Indeed, the unraveling began once the U.S. withdrew from Vietnam. The loss of American credibility which the withdrawal triggered, along with domestic political churn, created the strategic space for a string of Soviet successes in Africa and Central Asia, culminating with the Soviet invasion of Afghanistan. 

The Soviet Union, in 1980, was near its geostrategic goal of overturning the European balance through a major war. Only a military buildup that provided the U.S. with the forces to hold the Eurasian rimland in its entirety prevented that war.

Thus, Kabul can be seen as today’s Saigon. But, unlike in the 1970s, the United States faced an immediate test after it — Russia’s invasion of Ukraine. The U.S. response has been moderately effective; it has ensured a united European coalition and sustained Ukraine (so far) through a brutal existential fight. 

In doing so, the U.S. has followed the opposite path of Vietnam: It has manned the distant rampart with no blood of its own, and only a pittance of treasure, thereby tying down and undermining one of the three consequential members of the Moscow-Tehran-Beijing axis. 

But retreat in Ukraine — or a hasty settlement of any kind — will trigger a future crisis. 

The military balance in the Taiwan Strait is exceptionally close. The greatest factor that will undermine U.S. deterrence over Taiwan is not any specific military capability: Pouring every American resource into the Indo-Pacific would not necessarily tip the scales, given the primarily air-naval contours of such a fight. Rather, American credibility is paramount in the short-term — and an America unwilling to hold the line in Europe will be at greater risk in Asia.

Seth Cropsey, president of the Yorktown Institute, served as a naval officer and as deputy undersecretary of the Navy and assistant secretary of Defense during the Reagan and George H.W. Bush administrations. He is the author of “Mayday: The Decline of American Naval Supremacy” (2013) and “Seablindness: How Political Neglect Is Choking American Seapower and What to Do About It” (2017).

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