Hardtack (or hard tack) is a simple type of cracker or biscuit, made from flour, water, and sometimes salt. Inexpensive and long-lasting, it was and is used for sustenance in the absence of perishable foods, commonly during long sea voyages and military campaigns.

Army Hardtack Recipe
Ingredients:

4 cups flour (perferably whole wheat)
4 teaspoons salt
Water (about 2 cups)
Pre-heat oven to 375° F
Makes about 10 pieces
Mix the flour and salt together in a bowl. Add just enough water (less than two cups) so that the mixture will stick together, producing a dough that won’t stick to hands, rolling pin or pan. Mix the dough by hand. Roll the dough out, shaping it roughly into a rectangle. Cut into the dough into squares about 3 x 3 inches and ½ inch thick.

After cutting the squares, press a pattern of four rows of four holes into each square, using a nail or other such object. Do not punch through the dough. The appearance you want is similar to that of a modern saltine cracker. Turn each square over and do the same thing to the other side.

Place the squares on an ungreased cookie sheet in the oven and bake for 30 minutes. Turn each piece over and bake for another 30 minutes. The crackers should be slightly brown on both sides.

The fresh crackers are easily broken but as they dry, they harden and assume the consistentency of fired brick.