An exclusive golf course backs onto a spacious two-storey house. A coiled green garden hose lies on the lawn. The grey-slatted wooden shutters are closed. And, like the other deserted luxury houses in this gated community near Bryan, Texas, nothing moves.

Retired Colonel Jim Steele, whose military decorations include the Silver Star, the Defence Distinguished Service Medal, four Legions of Merit, three Bronze Stars and the Purple Heart, is not at home. Nor is he at his office headquarters in Geneva, where he is listed as the chief executive officer of Buchanan Renewables, an energy company. Similar efforts to track him down at his company’s office in Monrovia are futile. Messages are left. He doesn’t call back.

For over a year the Guardian has been trying to contact Steele, 68, to ask him about his role during the Iraq war as US defence secretary Donald Rumsfeld’s personal envoy to Iraq’s Special Police Commandos: a fearsome paramilitary force that ran a secret network of detention centres across the country – where those suspected of rebelling against the US-led invasion were tortured for information.

On the 10th anniversary of the Iraq invasion the allegations of American links to the units that eventually accelerated Iraq’s descent into civil war cast the US occupation in a new and even more controversial light. The investigation was sparked over a year ago by millions of classified US military documents dumped onto the internet and their mysterious references to US soldiers ordered to ignore torture. Private Bradley Manning, 25, is facing a 20-year sentence, accused of leaking military secrets.

Steele’s contribution was pivotal. He was the covert US figure behind the intelligence gathering of the new commando units. The aim: to halt a nascent Sunni insurgency in its tracks by extracting information from detainees.

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