It was hauled across the seven seas, borne into battle by Civil War soldiers and crumbled into an ocean of chowder. Now hardtack, a hard rectangular biscuit about as tasty as a rucksack, has been saved from the corporate cost cutters at Nabisco. Nine months after baking its last Crown Pilot Crackers, Nabisco is bringing back the 205-year-old product under pressure from New Englanders. About 3,500 people wrote or called Nabisco in protest after it stopped making the crackers in May. They were sold only in Maine, Massachusetts and New Hampshire, one of 300 "niche" brands eliminated as part of a corporate restructuring. Crown Pilot Crackers were a small but steady seller for Nabisco, accounting for about $500,000 of its $8.8 billion in annual sales.