'Cutting-edge' weapons no longer the Holy Grail.

• Author: Erwin, Sandra I.

It has been gospel at the Defense Department that for every major category of military hardware in the arsenal, there would be an exotic, shiny replacement in some stage of development.

Defense technology for decades has progressed on a linear path, from one generation to the next, always on the premise that the future would bring something bigger and better.

That tech-happy zeitgeist is from an era that now seems long gone. Ten years of grinding counterinsurgency wars, big-ticket research programs that failed to deliver combat-ready products and a rapidly rising national debt have transformed the mindset of what it means to design cutting-edge weapons.

It's not as if the military doesn't need innovation. Commanders for years have been asking for new and improved technology to combat roadside bombs and to find wily enemies who hide in bunkers. They also are seeking smarter munitions that hit targets precisely without killing innocent bystanders.

The Army, Marine Corps, Air Force and Navy also are saddled with aging fleets of ground vehicles, aircraft and ships that have been kept in service far longer than planned and ought to be replaced sooner, rather than later, officials say.

The defense budget has doubled since 9/11, and yet much of the military's hardware has not been modernized in decades. Many of the next-generation programs that the Pentagon has funded in its nearly $80 billion a year research-and-development budget have failed to produce new hardware, at least in large enough quantities to rebuild the fleet. By most accounts, the problem has not been lack of money, but the failure of the Pentagon's bureaucracies to turn promising concepts into equipment that troops find useful.

Symbols of an era of vibrant spending but stagnant modernization include the Army's Future Combat Systems, the Navy's DDG-1000 destroyer and the Marine Corps' Expeditionary Fighting Vehicle. All three programs were technologically ambitious but ill suited to a time when there is decreasing tolerance for decades-long development cycles and spiraling costs.

The Air Force fleet has been described by former deputy chief of intelligence, Lt. Gen. David Deptula, as "geriatric." Officials had envisioned the F-22 air superiority fighter as the centerpiece of the 21st Century fleet, but rising costs truncated the program. With current aircraft averaging nearly 25 years of age, the Air Force is in a modernization limbo, as it waits for the F-35 Joint Strike Fighter and a new air-refueling tanker that is not likely to offer any major leaps in technology compared to the Cold War-era KC-135.

The wars of the past decade, meanwhile, have exposed an "innovation gap" that has forced the U.S. military to play catch...