The voices on the tape are clear, but they betray a sense of anticipation and even excitement. Secretary of Defense Robert McNamara, the “whiz kid” technocrat recruited to the cabinet from the Ford Motor Co. three years earlier, speaks in precise, clipped tones. President Lyndon Johnson listens carefully and responds decisively. It is 9:43 on the morning of August 4, 1964.

It is worth eavesdropping on this conversation 55 years later, as tensions rise in the Strait of Hormuz, and the inarticulate grunts that make up the White House’s policy on Iran become increasingly bellicose. There is a lesson to be learned from the Gulf of Tonkin Incident: that the world’s most potent military power does not act spontaneously, and that the kind of provocation that will likely lead to the coming war with Iran is never unexpected, but carefully manipulated.

Few people knew the content of that telephone call, or of the others between August 2 and August 4 1964. They were not declassified until fifteen years ago. But now we can listen as the president and the secretary of defense coolly discuss the cynical machinations that would plunge the United States into a war that would last almost a decade, and kill 58,000 Americans and millions of Vietnamese and Cambodians.

McNamara advises against sending a US Navy destroyer, the USS Maddox closer to North Vietnam’s coast “to make clear that we believe the twelve-mile limit is not an effective limit on us… we think we do that adequately by sailing at eleven miles as opposed to eight.” Although it would not be formally embodied in international law until the 1980s, North Vietnam, like most coastal nations, including the United States, claimed jurisdiction over territorial waters up to 12 nautical miles off of its coasts. The US government well knew this, and sailed its warships within that 12-mile limit as an intentional provocation.

Neither the United States nor South Vietnam were at war with North Vietnam, but US navy ships had been buzzing the North Vietnamese coast on so-called DESOTO surveillance missions since 1962, and Hanoi was becoming increasingly edgy. There were tense moments over these years, as North Vietnamese gunboats would speed from their bases to confront the challenge to their territorial waters. Their commanders kept their cool and invariably held their fire as the American ships came about and steamed back across the 12-mile limit in a tacit recognition of North Vietnamese sovereignty.

But things were different in early August, 1964. Now, the United States was spoiling for a fight.

It was a fight that officials in the Pentagon, State Department, and the Central Intelligence Agency had been planning for since the beginning of the year. South Vietnam, the US-supported rump state created in 1955, had become a problem. Ngô Đình Diệm, our once-reliable puppet, had been deposed and murdered in a US-approved military coup in November 1963 once he had outlived his usefulness. South Vietnam’s new military junta was unable to get a grip on a political situation that had deteriorated rapidly since the National Liberation Front, with material support from North Vietnam, began an armed struggle in 1959.

Diệm had failed to stamp out South Vietnam’s expanding civil war, and received a bullet to the head in the back of an army truck for his efforts. The junta just brought more chaos, so the CIA enthusiastically supported a second coup in January that brought General Nguyễn Khánh to power as the country’s supreme leader. US officials liked Khánh; a cynical opportunist, he was the kind of person Johnson and McNamara could work with. But the situation in South Vietnam remained unstable.

“Khanh himself is a very able man within his experience,” McNamara observed in a top-secret memorandum to Johnson in March 1964, “but he does not yet have wide political appeal and his control of the army itself is uncertain.” Meanwhile, the civil war continued; the NLF had direct control over 40 percent of South Vietnam’s territory, and up to 90 percent of the territory of five provinces. “The stakes are high,” McNamara wrote. If the US could not stabilize the situation “almost all of Southeast Asia will probably fall under Communist dominance.” The secretary of defense concluded that the time had come for the United States to intervene in the South Vietnamese civil war and “initiate direct military action” against North Vietnam – and he had a plan to do it.

It was a cunning plan; it had to be. McNamara recognized that “U.S. intervention on a larger scale” could “disturb key allies and other nations.” He recognized that the Johnson administration could not act without a veneer of justification – what a later administration would call “plausible deniability” – without disturbing global and domestic public opinion.

Two days later, in National Security Action Memorandum 288, the administration officially adopted McNamara’s plan. The US would seek provocations to provide the justification to initiate, within 72 hours, “’Retaliatory Actions’ against North Vietnam, and to be in a position on 30 days’ notice to initiate the program of ‘Graduated Overt Military Pressure’ against North Vietnam.”

NSAM 288 rejected the proposal of “a full takeover of the command in South Vietnam by the U.S..” but only “for the time being.”

So the US escalated an undeclared covert war, hoping to irritate North Vietnam through a thousand pinpricks into open provocation. The Military Assistance Command, Vietnam – Studies and Observations Group (MACV-SOG), a classified, inter-service special operations unit, received orders to pick up the pace. Under OPLAN 34A (Operation 34-Alpha), South Vietnamese commandos, supported by the US Army, US Navy SEALs, and CIA black-ops teams, carried out raids and kidnappings in North Vietnam, while US Navy warships like the USS Maddox and USS Tuner Joy pressed ever closer to the coast.

In the early morning hours of August 1, 1964, an OPLAN 34A demolition team raided a North Vietnamese radar installation on an island in the Gulf of Tonkin; the Maddox steamed past the next day. “We probably shot up a radar station and a few other miscellaneous buildings,” McNamara reported to the president. “And following twenty-four hours after that, with this destroyer in that same area, undoubtedly led them to connect the two events.”

North Vietnam sent out gunboats to investigate the violation of its territorial waters. Heavy fire from the Maddox and fighters from the USS Ticonderoga forced the vessels to retreat, killing four North Vietnamese sailors and injuring about a dozen others. The Maddox sustained no damage or casualties. The destroyer was ordered, along with the Turner Joy, back into North Vietnamese waters on the night of August 3, to “show the flag” and, one must conclude, create another provocation.

Indeed, a classified report prepared by Pentagon analysts Marshall Wright and Sven F. Kraemer for the Defense Department’s Vietnam Information Group in 1964 noted that there was an OPLAN-34A raid planned to coincide with the “show the flag” mission:

During the night of August 3-4 Tonkin time South Vietnamese 34A operations were carried out against North Vietnamese shipping installations just north of the 17th parallel. At the time of these attacks the Maddox and the Turner Joy were patrolling an area of the Gulf of Tonkin approximately 70 miles to the northeast of the South Vietnamese attacks.

The USS Maddox made radar contact with five North Vietnamese torpedo boats approaching at high-speed. Captain John Herrick would later speculate that they had been waiting for the US ships. No shots were fired, but Wright and Kraemer noted that “a flash message was received in Washington reporting that the U.S. destroyers… were actually under attack.”

It was after this that McNamara and Johnson had their fateful 9:43 telephone conversation. The president still wasn’t sure that he had enough to start a war with, and suggested an escalation of the OPLAN-34A commando missions.

Johnson: But when they, when they move on us, and they shoot at us, I think we not only ought to shoot at them, but almost simultaneously, uh, uh, pull one of these things that you’ve, you’ve been doing –

McNamara: Right.

Johnson: – on one of their bridges or something.

McNamara: Exactly. I, I quite agree with you, Mr. President.

In the call, McNamara repeatedly recommends that the president wait for further provocation, a “second attack,” before launching airstrikes on North Vietnam and asking Congress for authorization to go to war. “I personally would recommend to you, after a second attack on our ships, that we do retaliate against the coast of North Vietnam some way or other.” Before ending the call, McNamara lays out the situation:

I’ve talked to [National Security Advisor] Mac Bundy a moment ago and told him that I thought that was the most important subject we should consider today, and, and be prepared to recommend to you a response, a retaliation move against North Vietnam in the event this attack takes place within the next six to nine hours.

The secretary of defense could only be so precise about a North Vietnamese attack that had not yet happened – “within the next six to nine hours” – and which would provide the final, irrefutable justification for American retaliation, only because he knew it was coming. He had already set events in motion that would produce the desired outcome, and plunge the United States into war. It was a set-up, and North Vietnam took the bait. A little over an hour later, McNamara was able to call the president with the good news: “President, we just had word by telephone from Admiral Sharp that the destroyer is under torpedo attack.”

But there was no attack. Captain Herrick would cable the Pacific Fleet headquarters:

“Review of action makes many reported contacts and torpedoes fired appear doubtful. Freak weather effects on radar and overeager sonarmen may have accounted for many reports. No actual visual sightings by Maddox. Suggest complete evaluation before any further action taken.”

McNamara did not pass this assessment on to the president. In any event, the wheels were already in motion. Later that night, President Jonson spoke to the nation in a televised address. In grave tones, he informed his fellow citizens that “hostile actions against United States ships on the high seas in the Gulf of Tonkin have today required me to order the military forces of the United States to take action in reply.” The words “high seas” suggested that the incident had occurred in international waters, in clear violation of international maritime law.

Few Americans questioned this, and three days later, the House of Representative voted unanimously to grant the President carte blanche “to take all necessary measures to repel any armed attack against the forces of the United States and to prevent any further aggression.” The Senate passed the resolution with only two dissenting votes, and the United States entered the Vietnam War.

It can be difficult to remember today – after 1968, Woodstock, and Kent State – that Americans overwhelmingly supported the war. Johnson went into the 1964 election three months later as the odds-on favorite, and won one of the greatest landslide victories in US history, carrying 44 states and the District of Columbia. To be sure, his enormous popularity was based more on domestic policies and continued economic growth. But the war didn’t hurt.

The New York Times, which had expressed skepticism about Johnson’s foreign policy acumen and his ability to manage the situation in Southeast Asia at the end of July, had no such doubts at the beginning of August. In an editorial on August 6 that articulated the nation’s mood, the Times threw its support behind the coming war as a virtuous crusade consistent with the best of American values:

We still have no real idea of what prompted the North Vietnamese to launch their potentially suicidal adventure. The nation’s unified confidence in its Chief Executive is vital. No one else can play the hand. That confidence will be best maintained by a continued adherence to the principles the President himself has enunciated of firmness, but a firmness that will always be measured – a firmness whose mission is peace.

Looking back, the Times’ editorial and American public confidence in the overwhelming rightness of the war seems absurd. But that was before Daniel Ellsberg leaked the Pentagon Papers, before the revelation of the secret bombing of Cambodia. It was before we could hear the voices of McNamara and Johnson as they discussed the clinical details of their long-hatched plan; as the trap snapped shut.

We don’t have the benefit of declassified documents and telephone conversations to know the details of the current administration’s plan is in the Strait of Hormuz, but we can be sure that even this administration has a plan. In one of the first public statements of his brief tenue as National Security Advisor, Michael Flynn pointedly put Iran “on notice” more than two years ago.

The US withdrawal from the Iran Nuclear Agreement, or Joint Comprehensive Plan of Action, seemed absurdly counter-productive a last year. All evidence indicated that Iran was in full compliance. “I can state that Iran is implementing its nuclear-related commitments,” International Atomic Energy Agency Director General Yukiya Amano said two months before the US withdrawal. “The JCPOA represents a significant gain for verification. It is essential that Iran continues to fully implement those commitments. If the JCPOA were to fail, it would be a great loss for nuclear verification and for multilateralism.”

But the US withdrawal did allow Washington to tighten the screws of economic sanctions, giving Tehran little reason to remain in compliance, while ratcheting up the kind of desperation that leads to rash decisions. And every accusation and provocation since has seemed calculated to produce a rash decision, by flying a drone into Iran’s airspace, or promoting a muddled – and even doubtful – account of attacks on shipping in the Strait of Hormuz.

And the Strait, like the Gulf of Tonkin 55 years ago, is where the plan will inevitably unfold. This waterway, crucial to the supply of petroleum sailing from ports in the Persian Gulf, is impossibly narrow, forcing ships to pass through Iranian territorial waters. They are permitted to do so under international maritime law, but even this “transit passage” has limits, and all indications are that Washington is eager to test and, if history is any indication, cross them.

Using the flimsy pretext of doubtful accusations, Secretary of State Mike Pompeo is aggressively pressuring America’s allies to join “Sentinel,” a US-led naval patrol in the Strait of Hormuz and the Persian Gulf. None have accepted the invitation to sign onto a plan that could only inflame the kind of tensions and lead to the incident in the Tonkin Gulf. Even the sober New York Times has wondered if Sentinel could spark a resumption of the Tanker War of the 1980s.

But that seems to be the point. As confused and indecisive as the current President of the United States might be, war with Iran might not be up to him. We cannot count on his stupidity to preserve the peace when war has been his most senior advisors’ persistent goal. More than a year before the 2016 election, and two years before he became the president’s National Security Advisor, John Bolton made his intentions absolutely clear.

“The inconvenient truth is that only military action like Israel’s 1981 attack on Saddam Hussein’s Osirak reactor in Iraq or its 2007 destruction of a Syrian reactor, designed and built by North Korea, can accomplish what is required,” He wrote in a New York Times op-ed in March 2015. “Time is terribly short, but a strike can still succeed.” The hunger for war has been there since the beginning; it is inconceivable that Bolton, Pompeo and their confederates do not have a plan now that they have the controls of the world’s most awesome war machine in their hands.

As in the Gulf of Tonkin in 1964, it is only a matter of time before the plan pays off. There will be war with Iran.