Key point: Iran keeps upgrading its precious F-14s to keep them flying and relatively modern.

On April 9, 1972, Iraq and the Soviet Union signed an historic agreement. The USSR committed to arming the Arab republic with the latest weaponry. In return for sending Baghdad guns, tanks and jet fighters, Moscow got just one thing — influence … in a region that held most of the world’s accessible oil.

In neighboring Iran, news of Iraq’s alliance with the Soviets exploded like a bomb. Ethnically Persian and predominately Shia, Iran was — and still is — a bitter rival of Iraq’s Sunni Arab establishment, which during the 1970s dominated the country’s politics.

In Tehran, King Mohammad Reza Shah Pahlavi — the “shah” — moved quickly to counter Baghdad’s move. First he set loose an army of secret police in a desperate and bloody bid to quell internal dissent. And then he reached out to the United States.

The shah wanted weapons. And not just any weapons. Himself a former military pilot, the king wanted the latest and best U.S.-made warplanes, with which the Iranian air force might dominate the Persian Gulf and even patrol as far away as the Indian Ocean.

The Iranian leader’s appetite for planes was notorious. “He’ll buy anything that flies,” one American official said of the shah. But Pahlavi was especially keen to acquire a fighter that could fly fast enough and shoot far enough to confront Soviet MiG-25 Foxbat recon planes that had been flying over Iran at 60,000 feet and Mach 3.

The administration of U.S. president Richard Nixon was all too eager to grant the shah’s wish in exchange for Iran’s help balancing a rising Soviet Union. Nixon and his national security adviser Henry Kissinger visited Tehran in May 1972 — and promptly offered the shah a “blank check.” Any weapons the king wanted and could pay for, he would get — regardless of the Pentagon’s own reservations and the State Department’s stringent export policies.

That’s how, starting in the mid-1970s, Iran became the only country besides the United States to operate arguably the most powerful interceptor jet ever built — the Grumman F-14 Tomcat, a swing-wing carrier fighter packing a sophisticated radar and long-range AIM-54 Phoenix air-to-air missiles.

It’s fair to say American policymakers quickly regretted giving Iran the F-14s. In February 1979, Islamic hardliners rose up against the shah’s police state, kidnapping 52 Americans at the U.S. embassy in Tehran and ushering the return of Ayatollah Ruhollah Khomeini. The Islamic Revolution transformed Iran from an American ally to one of the United States’ most vociferous enemies.

An enemy possessing 79 of the world’s most fearsome interceptors.

For the next five decades, the United States would do everything in its power — short of war — to ground the ayatollah’s Tomcats. But the Americans failed. Through a combination of engineering ingenuity and audacious espionage, Iran kept its F-14s in working order — and even improved them. The swing-wing fighters took to the air in several conflicts and even occasionally confronted American planes.

Today Iran’s 40 or so surviving F-14s remain some of the best fighters in the Middle East. And since the U.S. Navy retired its last Tomcats in 2006, the ayatollah’s Tomcats are the only active Tomcats left in the world.

The F-14 was a product of failure. In the 1960s, the Pentagon hoped to replace thousands of fighters in the U.S. Air Force and Navy with a single design capable of ground attack and air-to-air combat. The result was the General Dynamics F-111 — a two-person, twin-engine marvel of high technology that, in time, became an excellent long-range bomber in Air Force service.

But as a naval fighter, the F-111 was a disaster. Complex, underpowered and difficult to maintain, the Navy’s F-111B version — which General Dynamics built in cooperation with carrier-fighter specialist Grumman — was also a widowmaker. Of the seven F-111B prototypes that the consortium built starting in 1964, three crashed.

In 1968, the Defense Department halted work on the F-111B. Scrambling for a replacement, Grumman took the swing-wing concept, TF-30 engines, AWG-9 radar and long-range AIM-54 missile from the F-111B design and packed them into a smaller, lighter, simpler airframe.

Voila — the F-14. The first prototype took off on its inaugural flight in December 1970. The U.S. fleet got its first Tomcats two years later. Grumman ultimately built 712 F-14s.

In 1974, the shah ordered 80 of the fighters plus spare parts and 284 Phoenix missiles at a cost of $2 billion. Seventy-nine of the Tomcats arrived before the Islamic Revolution forced the shah into exile in Egypt and compelled the United States to impose an arms embargo. The U.S. Navy eventually scooped up the 80th plane for one of its test squadrons.

The U.S. State Department oversaw the F-14 transfer and, in its eternal wisdom, delegated most of the work to the Air Force. But the F-14 was a Navy plane and only the Navy had pilots qualified to fly the machine. The sailing branch seconded Tomcat crews to the flying branch, but only after extensive security checks lasting six months — and not without some culture clash.

The Navy pilots picked up the brand-new Tomcats at the Grumman factory in Long Island, New York and flew them three at a time to Iran. “Few pilots in their careers ever have the opportunity to fly an airplane that ‘smells’ exactly as a new car, and still has cellophane covering the cushions of the ejection seat,” one F-14 flier wrote years later. “Well, I had that amazing experience.”

“Although my F-14 was ‘factory fresh,’ it had an Iranian specified camouflage paint scheme. And while it did have U.S. military markings, as I found out later, those markings would be ingeniously and quickly changed upon arrival in Iran. The U.S. paint easily disappeared when a certain solution was applied, thus exposing the Iranian air force markings underneath.”

The journey to Iran involved two legs — from Long Island to Torrejon, Spain, and then onward to Iran’s Isfahan air base, with Air Force KC-135 aerial tankers constantly attending to the F-14s.

It was a complex and, for the pilots, uncomfortable undertaking. “We needed to be ‘topped-off’ with fuel for most of the seven-hour flight in case we had to divert to an emergency field,” the ferry pilot wrote.

“This meant at least six in-flight refueling events for each leg, despite some weather conditions — and the KC-135’s difficult, Rube Goldberg type of refueling hose to accommodate Navy aircraft.”

Air Force planes refuel in mid-air via a probe extending from the tanker into the receiving plane’s fuselage — the tanker crew does most of the work. Navy aircraft have their own probes and refuel by maneuvering the probe into a basket dangling from the tanker’s underwing fuel pods. The receiving pilot does the work — an arrangement consistent with the incredibly high demands the Navy traditionally places on its combat pilots.

To make the KC-135s compatible with the F-14s, the Air Force awkwardly fitted a basket to the tankers’ probes. The improvised contraption tended to whip around in the air, threatening to smash the Tomcats’ canopies every time they refueled.

Keeping gassed up wasn’t the only source of stress for the Tomcat ferry crews. “People often wonder, and it is rarely discussed — how did you relieve yourself, strapped into an ejection seat and immobile for seven-plus hours?” the pilot wrote.

The Navy offered the fliers diapers, but some refused to wear them. “I personally held it for seven hours … as I had planned and for which I had prepared by remaining dehydrated. Hey, I’m a fighter pilot.”

“However, upon arrival in Torrejon, I could barely salute the welcoming Air Force colonel,” the pilot continued. “Bending over and doubled-up under pressure, I feverishly ran to the nearest ‘head’ to relieve myself — for seemingly and refreshingly forever, before I could then return to properly meet, greet and properly salute the receiving Air Force colonel.”

While the U.S. Air Force and Navy worked together to deliver Iran’s F-14s, the State Department arranged for Iranian aviators and maintenance technicians to get training on the Tomcats and their complex systems. Some of the Iranians attended classes in the United States, others received instruction from American contractors in Iran. By 1979, the Americans had trained 120 pilots and backseat radar intercept officers.

The shah’s Tomcat squadrons were coming to life. But the Iranian king wasn’t entirely happy with his acquisition. In late 1975, the shah complained to the U.S. embassy in Tehran that Grumman had paid agents in Iran $24 million to facilitate the F-14 sale. The shah considered the payments bribes — and wanted Grumman to take the money back.

“Shah views with bitter scorn corrupt practices of agents for U.S. companies and ineffective [U.S. government] efforts to deal with problem,” the embassy reported back to Washington in January 1976. The shah was so angry that he threatened to halt payments to Grumman. Washington reminded Tehran that failure to pay would amount to breach of contract.

“The dispute over agents fees was poisoning U.S.-Iranian relations,” American diplomats in Tehran warned. Amid the diplomatic tension, Tehran put its Tomcats to good use performing the mission for which Iran originally wanted them — deterring the Soviet Union’s MiG-25 spy planes. In August 1977, Iranian F-14 crews shot down a BQM-34E target drone flying at 50,000 feet. “The Soviets took the hint and Foxbat over flights promptly ended,” Iranian air force major Farhad Nassirkhani wrote.