Navy submariners completed their move into the nuclear age Monday with the decommissioning of the USS Blueback, the last American attack sub to run on conventional power.

Eleven former skippers of the Blueback, including the first captain to take the brand-new diesel-electric-powered sub to sea in 1959, were on hand to say farewell to the remaining holdout against Adm. Hyman G. Rickover's nuclear Navy."This is the end of a military era. We must give way to progress," said Robert H. Gautier, the retired captain who commissioned the sub.

With the Blueback (SS-581) officially in mothballs, the United States becomes the only nation defended at sea by an all-nuclear-powered active submarine fleet. A scaled-down diesel sub, the USS Dolphin, is still operated but only as a research vessel.

After the first nuclear submarine, the USS Nautilus, was launched in 1954, Rickover convinced the Pentagon to begin phasing out all remaining diesel subs on the grounds that diesel subs could not travel as fast or remain submerged as long.