Soldiers die in wartime. Charlotte Freeman knew that when her husband, Brian – a West Point graduate, world-class bobsledder and Army Reserve captain – went to Iraq in 2006. Patrick Farr knew it when his son Clay called home on his 21st birthday to say he’d been wounded by a roadside bomb in Iraq but not badly, so he’d be back in action right away. After Brian Freeman and Clay Farr were killed – Farr by another roadside bomb a week after he was first injured in 2006, and Freeman in an attack on the provisional U.S. military headquarters in Kerbala in 2007 – their families grieved terribly. Charlotte Freeman was left to raise two tiny children on her own. Patrick Farr mourned the grandchildren he would never have.

Every casualty of war is a tragedy. But in a 207-page complaint filed Monday in federal court in Brooklyn, Charlotte Freeman, Patrick Farr and about 200 other U.S. veterans and family members of slain soldiers claim that there was something different about certain attacks on U.S. troops in Iraq. These were not acts of war, according to the suit. They were acts of terrorism – operations supposedly executed by militant cells that received training and weapons in Iran, allegedly with the full knowledge of Iran’s government.

The militant groups — Hezbollah in Iraq, Asa’ib Ahl al-Haq and the Promised Day Brigades — were also supposedly financed by Iran through the Iranian Revolutionary Guards Corps’ Quds Force. And that, according to the new suit, is what makes the Freemans and the Farrs and the other victims of these supposedly Iran-sponsored operations not just casualties of war but also plaintiffs under the Anti-Terrorism Act of 1992.

The soldiers and their families assert that five gigantic European banks – HSBC, Standard Chartered, Credit Suisse, Royal Bank of Scotland and Barclays – conspired with four Iranian banks to evade U.S. sanctions on Iran. The end result of the conspiracy, according to the complaint, was that the Iranian banks were able to divert more than $100 million to Iran-sponsored militant groups to fund attacks on U.S. troops in Iraq.

RELATED: U.S. veterans sue banks, claim they should pay for Iraq attacks

For the case to move forward, the lawyers representing Freeman, Farr and the other plaintiffs – Gary Osen and Tab Turner, both experienced terror finance litigators – will have to surmount two significant hurdles, according to one of the few academic experts on the Anti-Terrorism Act, Notre Dame law professor (and former U.S. Treasury Department terror funding official) Jimmy Gurule. First, the Anti-Terrorism Act does not explicitly extend liability to alleged conspirators, Gurule said. The 2nd U.S. Circuit Court of Appeals, which has jurisdiction over this case, explicitly refused in its 2013 decision in Rothstein v. UBS to permit aiding and abetting claims under the ATA. If U.S. District Judge Dora Irizarry, who is overseeing the new case, applies similar reasoning to conspiracy claims, Gurule said, this case will be sunk.

Similarly, the professor said, the plaintiffs will have to show that the attacks were not executed “by reason of an act of war.” Wartime claims are exempted from the ATA, Gurule said, because the law was not intended “to give a private right of action to soldiers in a military conflict.” (All of the banks declined requests for comment.)

With Gurule’s skepticism in mind, let’s look at the complaint’s conspiracy assertions, which are based on the U.S. government’s money-laundering investigations of the banks named as defendants. In the past several years, all of the bank defendants have reached deferred prosecution deals with the U.S. Justice Department, as well as settlements with banking regulators, to resolve allegations that they helped Iran by masking information on international wire transfers. Those agreements addressed alleged money-laundering beyond Iran, but all of the banks have conceded that they processed wire transfers for Iran in violation of U.S. sanctions. (What the banks thought of the sanctions is another story; the complaint quotes, for instance, a 2006 Standard Chartered email in which a manager said of U.S. restrictions, “Who are you to tell us, the rest of the world, that we’re not going to deal with Iranians?”)

The U.S. government, however, has never alleged the final links in the conspiracy chain outlined in the new terror funding suit. The banks’ agreements with the U.S. government did not accuse them of funding terror operations, nor did the U.S. government tie the European banks to wire transactions with the militant groups that supposedly carried out attacks on U.S. soldiers in Iraq. Osen and Turner – who were part of the team of plaintiffs’ lawyers who won an Anti-Terrorism Act liability trial against Arab Bank this summer in federal court in Brooklyn – have fashioned the new suit as a conspiracy case because there is no direct evidence connecting the defendants to terror groups.

That’s a novel and untested theory. Osen, Turner and their co-counsel in the Arab Bank trial were able to show jurors evidence of Arab Bank transactions with alleged Hamas leaders. (Arab Bank, I should note, plans to appeal the liability finding.) So far, that wire transfer evidence doesn’t exist against the European banks. In an interview, Osen said he is nevertheless confident he can show a conspiracy. He described the new case as the inverse of the Arab Bank suit, in which the bank vehemently contested allegations of systemic compliance violations.

“Each of these defendants knowingly entered into agreements with Iran to alter, falsify or omit information in U.S. dollar wire transfers they sent through the United States,” Osen told me. “Each defendant understood that their conduct was part of a larger scheme engineered by Iran.” At the very least, Osen said, the European banks were “deliberately indifferent” to the consequences of facilitating transactions for Iranian banks.

Judge Irizarry and the 2nd Circuit will eventually decide whether Osen’s expansive interpretation of the ATA is correct. In the meantime, plaintiffs in the new suit told me they hope their case will spread the word about Iran’s alleged sponsorship of attacks on U.S. troops. “If we’re not at war with Iran, why are you killing my son?” said Farr.

The military, according to U.S. Army Colonel Joel Rayburn, a senior research fellow at the National Defense University and a former adviser to General David Petraeus in Iraq, has been sure of Iran’s involvement in the Iraq war for several years. Rayburn, who is not involved in the suit against the European banks, said that military intelligence identified three types of “signature” weapons that originated in Iran and were deployed against U.S. troops, including roadside bombs much more sophisticated than those used by Sunni insurgents in Iraq. Rayburn also said there’s copious evidence that Iranian military advisers directed attacks by militant groups.

“It’s clear to me that the Iranian regime was conducting a proxy war against our troops in Iraq in order to expel us from Iraq violently,” Rayburn told me. “There is no doubt.” According to the colonel, militant groups trained, armed and funded by Iran were probably responsible for about 2,000 roadside bomb attacks on U.S. troops, in addition to rocket and mortar attacks. Hundreds of soldiers, he said, were killed in Iran-sponsored attacks.

The military, Rayburn added, has been trying to tell that story since at least 2007, but met with “near complete skepticism and dismissal” from academics and analysts outside of the U.S. government.

But not from family members like Charlotte Freeman, whose husband died in one of the most intensively investigated incidents in the Iraq war. Freeman said she always thought there was “something weird” about the attack, in which operatives dressed as American soldiers and armed with American weapons stormed the U.S. compound in Kerbala and kidnapped four soldiers, including Brian Freeman. The four were subsequently executed and abandoned as attackers fled. “It was very sophisticated, very planned out,” she said. “It felt like a terrorist thing.”

Freeman said she knows war and just about everything else is complicated in the Middle East, but that she joined this case because she believes soldiers in wartime shouldn’t be targets of terror and financial institutions shouldn’t let them be.

“More than anything else,” she said, “I hope this case will make a statement.”

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(This post has been corrected. A previous version incorrectly described the Iranian Revolutionary Guards Corps’ Quds Force. This version also clarifies comments by Rayburn.)

PHOTO: The exterior of the Federal Court building is seen in the Brooklyn borough of New York, Nov. 16, 2012. REUTERS/Carlo Allegri