Now, more than 80 pages of newly declassified intelligence documents for the first time describe in detail an elaborate network used by Iraqis to gain entry into Iran and train under Iranian supervision. They offer the most comprehensive account to date to support American claims about Iranian efforts to build a proxy force in Iraq. Those claims have become highly politicized, with Bush administration critics charging that accounts of Iranian involvement have been exaggerated.

The prisoners’ accounts cannot be independently verified. Yet the detainees gave strikingly similar details about training compounds in Iran, a clandestine network of safe houses in Iran and Iraq they used to reach the camps and intra-Shiite tensions at the camps between the Arab Iraqis and their Persian Iranian trainers…

The documents portray an Iranian strategy to use Iraqi Shiites as surrogates, in part to avoid the risk of Iranians being captured in Iraq. In one of the intelligence reports, a prisoner tells his captors that “Iran does not want to fight a direct war” with American forces in Iraq because Tehran worries that the United States would destroy Iran…

The new Iran study, written by Mr. Fishman and Col. Joseph H. Felter, concludes that Iran aims to attack American troops in Iraq in part to show off its own abilities and in part to “demonstrate a credible deterrent against a U.S. strike on Iran’s nuclear facilities.”