The USS North Carolina was commissioned last weekend at a ceremony in Wilmington. The $2.5 billion attack sub will be based in New London, Conn. But Wilmington was an especially good place for the commissioning.

There, as every Tar Heel knows, is berthed the previous USS North Carolina, the much-admired battleship of World War II fame, now a memorial. For the record, there were two North Carolinas before that -- a 19th century 74-gun ship of the line, and an early-20th century armored cruiser.

The newest North Carolina is thoroughly 21st century. A Virginia-class attack submarine, the nuclear-powered boat (as subs are known) is intended to roam the seas stealthily and swiftly, attacking, if need be, targets above or below water, and, with cruise missiles, far away on land. Virginia-class subs are designed with a special focus on the shallower waters of seacoasts, near and far.

Is that worth the $2.5 billion price tag? National defense is always costly, sometimes excessively so. But even in a post-Cold War world, the world's oceans aren't assured permanent peace. The United States, long a maritime power and ever-more reliant on ocean shipping, has a vital interest in keeping the seas open -- and in retaining a technological edge on rising powers such as China.

The crew and captain of SSN 777 sail with best wishes from North Carolina.

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