The night Canadian Master Corporal Darrell Priede of Brantford died in Afghanistan, the Afghan war took a sudden dangerous new twist.

A stream of secret U.S. military intelligence reports released this week by the WikiLeaks website suggests the May 2007 death was the result of a Taliban attack with a heat-seeking, surface-to-air missile launched from the shoulder.

In all likelihood, the deadly weapon was provided by Iran.

Those two facts alone may be transforming the almost nine-year-old Afghan war.

Iran has long been suspected of covertly supplying arms to the Taliban, but the WikiLeaks data dump suggests it could now be almost as crucial to the Afghan insurgency as Pakistan.

Summaries of classified U.S. military and diplomatic reports among the documents demonstrate a growing concern over Iran's influence in Afghanistan and catalogue fears Iran's Revolutionary Guard is waging a secret campaign to arm, train, fund and equip the Afghanistan insurgency.

Master Cpl. Priede's death may have been a point of convergence for those fears.

Early on the evening on May 30, 2007, the Canadian military photographer accompanied a combined force of British paratroopers and members of the U.S. 82nd Airborne Division on a night assault on suspected Taliban positions near the Kajaki dam in Helmand province.

The dam, a strategic part of plans to rebuild Afghanistan, was undergoing repairs to provide electricity for about two million people in the Kandahar region.

Master Cpl. Priede, who documented combat operations, was returning from the battlefront with a British photographer and the five U.S. crew members of a twin-rotor, heavy-lift Chinook helicopter, when the big chopper was hit in the left rear engine by a missile.

It burst into flames and nose-dived into the ground, killing everyone on board.

Not long afterward, a Taliban spokesmen gloated over the attack, bragging insurgents had used "new weapons" to destroy the Chinook.

NATO officials just as quickly dismissed the Taliban claim, insisting the helicopter was downed by a "lucky hit" by guerrillas firing a rocket-propelled grenade (RPG).

But the WikiLeaks documents show witnesses to the attack were certain the downed helicopter was hit by a "MANPAD" (Man-portable air-defence system).

"Based on description of launch, size of round, and impact force of the projectile, it is assessed to be bigger [than] an RPG and possibly a surface-to-air missile," an after-action report said.

Two Apache attack helicopters sent to hover over the crash site within 30 minutes of the attack also came under fire from hand-launched, heat-seeking missiles, which pilots described as "a probable first-generation MANPAD."

NATO commanders probably decided to downplay the attack to avoid comparisons to the Afghan mujahedeen's stunningly successful use of CIA-supplied Stinger surface-to-air missiles to shoot down dozens of Soviet Hind helicopters during the 1980s.

Historians generally say the introduction of Stingers drove Soviet aircraft from Afghanistan's skies during the mujahedeen's war against the Soviet Union's occupation.

The coalition's silence on an emerging missile threat may also have been intended to avoid suggestions NATO forces were being attacked with left-over U.S. Stinger missiles from the Soviet era and to protect a rash of new intelligence reports that said Iran was significantly stepping up aid to the Taliban and selected Afghan warlords.

According to the WikiLeaks documents, as early as September 2005, Taliban commanders in Zabul and Kandahar provinces were said to have acquired "No. 2 Stinger" missiles, which they bought for $1,000 each.

Another report in April 2007 said Iran purchased seven heat-seeking missiles from Algeria and clandestinely transported them to Afghanistan from the Iranian city of Mashhad.

Yet another report, as recent as January 2009, says Hussein Razza, an Iranian agent, arrived in Marjah, Helmand, with four Stingers.

Rahul Bedi, a longtime correspondent in South Asia with Jane's Defence Weekly, believes the Iranians are copying a successful U.S. Cold War strategy.

"I think the Iranians have probably learned from the experience of the CIA and the mujahedeen, and are trying to duplicate, more or less, a similar operation," he said.

Under severe international pressure to end its uranium enrichment program and nervous about being besieged by a growing U.S. military presence in Iraq, Afghanistan and Central Asia, Iran appears bent on increasing its leverage by supporting insurgents to tie down U.S. troops in a long, unpopular and costly war.

"I think Iran is playing all sides in the Afghan conflict," said Ahmed Rashid, an expert on Islamic militancy and author of a book on the Taliban.

"Tehran and the Taliban have a common enemy. I have no doubt that Iran has been involved in channelling money and arms to various elements in Afghanistan for the last few years."

For years U.S. officials have alleged --and Tehran has, just as fiercely, denied -- Iran is waging a proxy war in Afghanistan, similar to the strategy it adopted in Iraq.

Claims of Iranian interference have usually been based on seized Taliban caches of Iranian plastic explosives, mortars, grenades and technical manuals. But the WikiLeaks documents describe intelligence reports that show elements of Iran's Revolutionary Guard have undertaken a far-reaching campaign to support Taliban-and al-Qaeda-related insurgents.

"Since 2005, there has been a rise in Iranian links with the Taliban, mostly in the form of support for individual Taliban commanders, usually a handful in each southern province and stronger support in the west," said Antonio Giustozzi in a recent report for the New York-based Century Foundation.

"Initially, the Iranians limited themselves to providing medical supplies and limited quantities of weaponry and ammunition. But since 2008, there appears to have been a significant increase in supplies and, most noteworthy, the provision of training to groups of Taliban inside Iran."

Iran and the Taliban dislike each other. They have a history of animosity that almost erupted into war in the 1990s, when the Taliban's Sunni fundamentalists murdered thousands Afghan Hazara Shiites and killed 11 Iranian diplomats.

That hostile relationship has gradually become a more collaborative one as Iran's relations with the United States and the West deteriorated.

"As tensions between Washington and Tehran increase, Shiite antipathy for Sunni jihadists such as al-Qaeda and its Taliban allies may be outweighed by a desire to find ways to spoil U.S. interests in the region," Bruce Riedel of the Brookings Institution writes in the latest edition of the West Point Military Academy's combating terrorism newsletter, The Sentinel.

"The United States and Iran are on a collision course over Tehran's determination to develop a nuclear weapons' capability. As this confrontation worsens, Iran will be looking for ways to damage U.S. interests in the region, especially through means that bog the United States down further in Iraq and Afghanistan."