WASHINGTON — The U.S. Army is pressing into place sweeping changes in its basic training program, introducing rigorous new drills and intensive work on combat skills to prepare recruits for immediate missions to Iraq and Afghanistan.

In what senior officers describe as the most striking changes to basic training since the Vietnam era, soldiers whose specialties traditionally kept them far from the front — clerks, cooks, truck drivers and communications technicians — will undergo far more stressful training. The new training regimen includes additional time dodging real bullets, more opportunities to fire weapons, including heavy machine guns, and increasing the time spent practicing urban combat and hiking and sleeping in the field during the nine-week courses.

Before the Iraq war, freshly minted soldiers could expect months, if not years, of additional training within their assigned units before seeing combat.

But with the Army stretched today by long-term deployments to Iraq and Afghanistan, a growing percentage of new soldiers are in combat zones within 30 days of being assigned to a unit, Army officials say. Even those whose specialties are not combat arms often face situations where the traditional distinction between hazardous front lines and secure rear areas has vanished.

"Historically, combat support specialists had been in the rear of the battlefield, far from direct contact with the enemy," said Col. Bill Gallagher, commander of the basic combat training brigade at Fort Benning, Ga. "The emphasis in their training was more on the technical side of their specialties, not on the combat side."

But in the missions soldiers face today, "there is no front, there is no rear," he said. "Soldiers of all specialties will face direct contact with an adversary. They all have to have a common set of combat skills. A sense of urgency dictated that we analyze what skills are required of them in Iraq, or in Afghanistan, and how to update the nine-week program back in the States."

The changes were endorsed at a meeting of the Army's training brigade commanders in June and were promptly put into effect on an official, if still interim, basis at all five installations where the Army conducts its basic training.