OPERATION MULE SHOE 

BY JOHN PRADOS

Today, nearly 50 years after the end of the Vietnam War, many aspects of how the U.S. pursued the war remain in contention. One is the potential impact of an invasion of North Vietnam.

In the mid-1960s, some observers believed that a U.S. move into North Vietnam was a winning strategy; others dismissed it as an overextension of American military power and likely to trigger intervention by the People’s Republic of China. Some, including retired Army Gen. H. R. McMaster, have since criticized the Joint Chiefs of Staff for not proposing extreme options such invading North Vietnam to President Lyndon Johnson. Others, such as the late Army Col. Herbert Schlandler, criticized the Chiefs for constantly proposing large escalations of the war.

Today there is new evidence about the invasion debate from the Joint Chiefs of Staff themselves, courtesy of retired Army Col. Mark A. Viney, who says that JCS Chairman Gen. Earle Wheeler actually planned to invade North Vietnam. Mark Viney’s grandfather, George C. Viney, was a senior aide to Wheeler and the officer who compiled an invasion proposal at his request. Mark Viney’s 2021 book, Determined to Persist, includes interviews and notes from his grandfather; letters and papers from Wheeler’s wife Frances; and the declassified feasibility study for Operation Mule Shoe, as the proposed invasion of North Vietnam was dubbed.

In the spring of 1967 Wheeler told George Viney that President Johnson was frustrated with his senior leadership, particularly Secretary of Defense Robert S. McNamara. It was a time of reflection as the high command struggled to devise a Vietnam War strategy that offered hope of success, could be executed efficiently, and would be acceptable to LBJ.

The Pentagon was considering another round of troop deployments and a strategic Vietnam War policy review was being prepared for Johnson. Already on the table was the idea of a defensive line across the Demilitarized Zone which separated South from North Vietnam, a concept codenamed Practice Nine — later known as the McNamara Line — that LBJ had approved in January 1967.

Gen. William C. Westmoreland, the commander of U.S. forces in Vietnam, came to Washington to participate in the Vietnam War strategy review. At an April 26 meeting with LBJ, Westmoreland presented the case for an invasion of Laos spearheaded by South Vietnamese troops. In that same meeting Johnson’s national security adviser Walt Rostow pushed for an invasion of North Vietnam. Wheeler sat mostly silent.

Independently of all this, Wheeler pursued his concept of an invasion. He chose Col. Viney as action officer for the Joint Chiefs of Staff in assembling a preliminary study, which Wheeler ordered on March 6, 1967. Wheeler envisioned the invasion as a disruptive stirring of the pot, a sudden incursion that would block North Vietnamese troop and supply movements. He would then withdraw American forces before Hanoi could move against them.

In early discussions the JCS chairman hinted at occupying a slice of North Vietnam as a negotiation chip, but never mentioned it in follow-up. The president’s concern over a Chinese ground attack made that idea a non-starter. Wheeler instructed Lt. Gen. Bernard Spivey of his staff to create a study group to explore the plan in more detail. Brig. Gen. V. W. Banning headed the ad hoc group. Viney was one of the lead planners.

The group also included 11 members of the Joint Chiefs Staff, a dozen staff experts from the military services, and two officers from the Defense Intelligence Agency. The study group had orders to keep U.S. global responsibilities unchanged, to leave stockpiles of North Atlantic Treaty Organization supplies untouched, to temporarily extend tours of duty for American troops in Vietnam, and not to call up the Reserves.

The North Vietnamese responded strongly to signs of an installation of the McNamara Line. Not long after Westmoreland went to Washington the North Vietnamese besieged Con Thien, one of the McNamara Line positions. In April, while the White House strategy deliberations were occurring, Marines at Khe Sanh, the westernmost American position below the DMZ, encountered North Vietnamese Army regulars on two hills overlooking the U.S. combat base. This was a place the McNamara Line was supposed to protect.

What became known as the Hill Fights followed during the final week of April. The first week of May brought a North Vietnamese assault on the nearby Special Forces camp at Lang Vei.

The fighting in I Corps crystallized a dilemma the Joint Chiefs, the Secretary of Defense, President Johnson, and other U.S. leaders had been wrestling with for months: the question of reinforcements for U.S. forces in South Vietnam. Westmoreland had pushed for more troops in 1967. The Joint Chiefs preferred to mobilize U.S. Reserve units, both to add combat power and as a signal that the United States took the conflict seriously.

President Johnson did not want to bring in Reserve units to avoid criticism that the Vietnam War had not been legally authorized, as well as to minimize the economic costs of the fighting, which were becoming a drag on the U.S. economy. McNamara maneuvered between the Chiefs and the President.

Almost every avenue of inquiry led back to manpower. The Pentagon, for example, studied sending two infantry divisions to Vietnam to take part in an invasion. But the study found that two-thirds of the Navy’s large landing craft in the Pacific, plus others operated by the Military Sea Transport Service, were already in use supplying Vietnam and that the Navy lacked sufficient amphibious shipping for a two-division force. So the invasion plan cut back the contingent that would land from the sea to a single division. The troops would either be mobilized or taken from units slated to reinforce NATO in Europe in the event of a Soviet attack there. Those were the only possibilities.

On April 10 the full Joint Chiefs of Staff met in their conference room to hear a briefing on the North Vietnam invasion project. Discussions went on for nearly four hours, longer than the usual JCS meetings.

The requirements for Mule Shoe became part of the Chiefs’ review of the U.S. worldwide military posture. They recommended activating seven additional Army and two Marine divisions, roughly equal to the entire U.S. force then in South Vietnam. The next day the Chiefs added intensified bombing of North Vietnam to their options list and the ad hoc study group went into high gear on April 21.

At this point Westmoreland arrived in Washington for the White House Vietnam War strategy talks. On April 26, Johnson famously pressed Westmoreland on whether North Vietnam, if the United States added divisions, would also increase its troop strength. Rostow debated Westmoreland on the desirability of a Laos operation versus invading North Vietnam. Westmoreland countered that an invasion of North Vietnam could only happen during the monsoon season that already was in progress, which meant the operation wouldn’t take place until 1968.

The Laos operation had to happen during the dry season, which required a postponement of half a year. Rostow said that if the U.S. was going to mobilize, troops should surely be used for something spectacular.

McNamara’s response came in a May 19 draft presidential memorandum. He pointed out that the majority of the strategic options were for actions outside South Vietnam. If the war’s center of gravity lay inside South Vietnam, he said, those options did nothing to affect it. There was no reason to believe that actions that took place in North Vietnam or in Laos would alter the balance either.

The Joint Chiefs responded with a raft of memoranda countering McNamara’s arguments. Rostow weighed in, saying that only the president could decide whether or not there would be a mobilization.

In this charged atmosphere the JCS study group on the feasibility of Mule Shoe completed its work. The Joint Chiefs gathered to hear the result on June 23. They met privately, without including the operations deputies who usually took part in high-level meetings. Col. Viney was the main presenter. Air Force Col. Ralph J. Hallenbeck took notes.

There could be no doubt this was an ambitious scheme. A full division, presumably the 3rd Marines, would attack through the DMZ. An airmobile division, likely the 1st Cavalry, would air assault into blocking positions in the North Vietnamese panhandle that separated the Annamite mountains from the coastal plain. The 82nd Airborne Division would parachute into blocking positions along an east-west axis below Dong Hoi.

The amphibious landing would be handled by a newly reconstituted Marine division, which would capture initial objectives and then sweep south to meet the assault across the DMZ. Both contingents would destroy enemy supply caches. The concept was for a two-week operation with eleven days of active maneuvers. The feasibility study projected 144 killed and 900 wounded per day, a total of 10,440 casualties.

There were plenty of questions about the set of hypotheticals. The airborne operation posed special problems. There had not been a division-sized air landing since World War II and no one knew if the military was ready for one now. Plus, virtually every U.S. C-130 and C-141 in Vietnam would have to be engaged for the duration of the offensive.

Gen. Harold K. Johnson, the Army chief of staff, and Wheeler had at it for several hours while the other members of the Joint Chiefs of Staff placidly approved the invasion concept. Wheeler understood that with Johnson’s approval on the line and the president’s unwillingness to challenge China, he could not propose an operation the Chiefs did not back unanimously.

Another result of the planning for Mule Shoe was that the Pentagon had the time to examine North Vietnam’s defenses in greater depth. A review completed in July showed real changes: North Vietnamese troops above the DMZ had tripled since 1965, to 41,000 in three divisions. In 1966 there had been three surface-to-air missile battalions in this part of North Vietnam. That number soon doubled. Plus, there were 452 antiaircraft guns in the region, a hundred of them within the invasion area.

In October, when antiwar protesters marched on the Pentagon, the military was no closer to recieving their ticket for passage to North Vietnam.

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