Abuja (AFP) - The claims read like the plot of a best-selling thriller, with secretive arms dealers and a corruption-riddled government fighting jihadists.
The weapons deal collapses in acrimony but instead of a shoot-out, the embittered parties fight it out in court.
In this real life saga, Ara Dolarian is the US arms dealer, Hima Aboubakar the weapons contractor and the foreign government Nigeria, which has been locked in a battle with Boko Haram since 2009.
The $246 million (221 million euros) order at the height of the jihadists' insurgency in 2014 was for weapons and equipment, including helicopters, bombs and ammunition.
It could have given over-stretched and under-resourced Nigerian troops a boost, as the better-armed rebels captured territory across northeast Nigeria, often without a fight.
But the deal collapsed in 2015 and the arms never arrived. Aboubakar sued Dolarian for fraud in California.
Aboubakar, a national of Niger, claimed the US arms dealer failed to ship $8.6 million worth of bombs and rockets, damaging his reputation as "a trusted arms supplier to the Nigerian military".
Dolarian alleges in court documents that he was unwittingly caught up in a "money laundering scheme" and that Aboubakar's arms money was "stolen from the Nigerian government".
- Rare glimpse -
Campaign group Transparency International described corruption in the defence procurement sector as "the new diesel for Nigeria's kleptocrats".
It estimated that more than $15 billion has been stolen, "leaving the military without vital equipment, insufficiently trained, low in morale and under-resourced".
"This has crippled the Nigerian military," it added in a new report published on Thursday, which defence spokesman John Enenche rejected and described as "a sweeping allegation".
The defence ministry now did "government-to-government" deals and no longer used contractors, he added.
The court battle between Dalorian and Aboubakar some 12,500 kilometres (8,000 miles) from Abuja offers a rare glimpse into the shadowy world of the arms trade.
It could also shed light on how an alleged multi-billion-dollar fraud in the office of former national security advisor Sambo Dasuki might have taken place.
Pieter Wezeman, a researcher at the Stockholm International Peace Research Institute, said Dolarian's deal with Aboubakar and his company Societe d'Equipments Internationaux (SEI) "rings alarm bells".
Court documents show SEI signed off on the purchase of six Mi-24 and Mi-35 helicopters from Dolarian for $25 million each, which Wezeman said was far above their normal value of $5 million each.
Inflated prices open the door to graft, he added. "This is really a ridiculous price," he said.
- Endemic corruption -
Current President Muhammadu Buhari's predecessor Goodluck Jonathan and his administration were forced to take Boko Haram seriously after the kidnapping of more than 200 schoolgirls from the remote town of Chibok.
The mass abduction in April 2014 drew the world's attention to the conflict, sending the government on a shopping spree for weapons.
Buhari, a former military head of state, honed in on the notoriously rotten defence procurement sector after coming to power on an anti-corruption platform in 2015.
Dasuki has been accused of orchestrating a sprawling embezzlement scheme that saw "phantom contracts" awarded for personal and political gain.
- Shocking scale -
The scale of the alleged scam and how officials apparently exploited the insurgency shocked even Nigerians wearily familiar with corruption scandals.
Dasuki and scores of other defence officials were arrested and put on trial. Buhari's government then went after procurement firms.
Last year, a committee set up by Buhari said SEI played a "major" role in the alleged scam after being awarded nearly $1 billion worth of contracts "characterised by irregularity and fraud".
SEI deals appear in many ongoing corruption cases in Nigeria.
Two top air force officials are charged with bribery for accepting cash and a Range Rover from the company.
Aboubakar has not been charged and told AFP: "We continue to work with the Nigerian army. Forget about what the people say, they lie."
- 'Excessive secrecy' -
Repeated adjournments have become a feature of the separate trials linked to the Dasuki "arms scam".
As time goes by without a big name conviction, there are doubts about whether a significant dent will be made in Nigeria's culture of corruption.
Buhari himself -- the driving force of the anti-graft campaign -- is wrestling with ill health.
Nigeria specialist Matthew Page said Buhari was not reforming a system of embezzlement "codified" by former military rulers such as Sani Abacha.
Habits that saw many senior officers get rich over decades of military rule persist, despite the return to democracy in 1999, he said.
Nearly two decades later, the defence sector is still secretive, with little or no oversight and transparency, and arms procurement still requires ad hoc approvals from the executive.
"Buhari is a dyed-in-the-wool military guy," said Page, a former US State Department official.
"All these issues, excessive secrecy and the notion that the military operates by different rules, these are principles that Buhari prescribes to pretty closely."