This article was reported by C. J. Chivers, Eric Schmitt and Nicholas Wood and written by Mr. Chivers.

Since 2006, when the insurgency in Afghanistan sharply intensified, the Afghan government has been dependent on American logistics and military support in the war against Al Qaeda and the Taliban.

But to arm the Afghan forces that it hopes will lead this fight, the American military has relied since early last year on a fledgling company led by a 22-year-old man whose vice president was a licensed masseur.

With the award last January of a federal contract worth as much as nearly $300 million, the company, AEY Inc., which operates out of an unmarked office in Miami Beach, became the main supplier of munitions to Afghanistan’s army and police forces.

Since then, the company has provided ammunition that is more than 40 years old and in decomposing packaging, according to an examination of the munitions by The New York Times and interviews with American and Afghan officials. Much of the ammunition comes from the aging stockpiles of the old Communist bloc, including stockpiles that the State Department and NATO have determined to be unreliable and obsolete, and have spent millions of dollars to have destroyed.