Background: The traditional seal used during and since the   Revolution was redesignated as the Seal of the Department of the Army by the   National Security Act of 1947. The Department of the Army seal is authorized by   Section 3011, Title 10, United States Code. The date "MDCCLXXVIII" and the   designation "War Office" are indicative of the origin of the seal. The date   (1778) refers to the year of its adoption. The term "War Office" used during the   Revolution, and for many years afterward, was associated with the Headquarters   of the Army. 
                        Description: In the center is a Roman cuirass below a vertical   unsheathed sword, point up, the pommel resting on the neck opening of the   cuirass and a Phrygian cap supported on the sword point, all between, on the   right an esponton and, on the left a musket with fixed bayonet crossed in   saltire behind the cuirass and passing under the sword guard. To the right of   the cuirass and esponton is a flag of unidentified designs with cords and   tassels, on a flagstaff with spearhead, above a cannon barrel, the muzzle end   slanting upward behind the cuirass, in front of the drum, with two drumsticks   and the fly end of the flag draped over the drumhead; below, but partly in front   of the cannon barrel, is a pile of three cannon balls. To the left of the   cuirass and musket is a national color of the Revolutionary War period, with   cords and tassels, on a flagstaff with spearhead, similarly arranged above a   mortar on a carriage, the mortar facing inward and in front of the lower portion   of the color and obscuring the lower part of it; below the mortar are two bomb   shells placed side by side. Centered above the Phrygian cap is a rattlesnake   holding in its mouth a scroll inscribed "This We'll Defend." Centered below the   cuirass are the Roman numerals "MDCCLXXVIII." 
                        Symbolism: The central element, the Roman cuirass, is a symbol   of strength and defense. The sword, esponton (a type of half-pike formerly used   by subordinate officers), musket, bayonet, cannon, cannon balls, mortar, and   mortar bombs are representative of Army implements. The drum and drumsticks are   symbols of public notification of the Army's purpose and intent to serve the   nation and its people. The Phrygian cap (often called the Cap of Liberty)   supported on the point of an unsheathed sword and the motto, "This We'll   Defend," on a scroll held by the rattlesnake is a symbol depicted on some   American colonial flags and signifies the Army's constant readiness to defend   and preserve the United States.