The arrest of a reputed arms dealer known as "The Field Marshal" is the latest success in a global cat-and-mouse game between federal agents and a network of shadowy business figures trying to smuggle weapons and equipment to Iran from the country most determined to stop them: the United States. Jacques Monsieur, a Belgian long pursued by various governments for shipping military supplies to trouble spots around the world, was arrested in late August after an undercover Immigration and Customs Enforcement investigation. He is accused of trying to buy fighter jet engines for Iran. His lawyer said he plans to plead not guilty. Monsieur's case - based on clandestine meetings in London and Paris before his arrest in New York - may be the most unusual among a slew of U.S. charges against people accused of trying to violate the arms embargo on Iran. Monsieur apparently was imprisoned for a time by Iranian authorities after skirting charges in Europe for several years and claiming in a 2004 interview he had an unspecified relationship with US intelligence officials. According to Pat Rowan, a former Justice Department official, Iran's ability to acquire such equipment depends on middle men operating "shady companies around the world." "It's an extraordinary network they've developed to work around the web of sanctions that's intended to stop them," he said. Often, those networks target U.S. suppliers, which are the best source of high-quality military equipment. "Our military technology is the foremost in the world in terms of quality and design and manufacture, so there's an obvious desire to obtain it," said Steven Pelak, deputy chief of the Justice Department's counterespionage section. "Are we ever going to completely stop it? No. Are we going to put a dent in it? Yes," he said. Pelak said recent successes with the United Arab Emirates in shutting down Iranian networks operating there have led some suspects to shift efforts to Malaysia. While many of the cases involve engine parts and equipment, those same networks could be used to obtain more deadly material, he said. "They are ready and willing to move all sorts of items," Pelak said. Charges filed against a variety of individuals outline what authorities call sophisticated and far-reaching attempts by Iran to evade sanctions and acquire restricted weapons technology, including: - A Toronto man charged with trying to get devices used with enriched uranium from a U.S. company in order to send them to Iran. - A man charged in California with overseeing an international network that allegedly purchased thousands of military and commercial items from US companies, shipping them through Malaysia to Iran. Authorities charge the material was sent to two Iranian military entities declared off limits by the US for their role in Iran's nuclear and ballistic missile program. - Electronic components allegedly sent to Iran that wound up in improvised explosive devices designed to kill US troops in Iraq. For years, the United States has tried to keep Iran from obtaining a wide range of materials. Most often, the investigations center around individuals trying to obtain parts for Iran's civilian and military aircraft. The stakes have been raised, though, as the West seeks to block Iran, which has been assisted partly by U.S. rivals, from further developing its ballistic weapons and nuclear capabilities. "We're talking about problems with Russia and China, but there's a problem in our own backyard," said Valerie Lincy, who closely monitors Iran's procurement as part of the Wisconsin Project on Nuclear Arms Control, a private group that seeks to stop the spread of weapons of mass destruction.