Staff Writer (Updated: 8/27/2014):
The M19, unveiled in 1942, was of a conventional mortar design by most respects and closely resembled the British 2-inch mortar family. The launch tube could accept projectiles of 60mm caliber with warheads to include high-explosive (HE), illumination and smoke rounds. The mortar crew was often charged with engaging dug-in enemies by raining munitions on or around them in an attempt to kill or dislodge. Beyond its lethal intent, the M19 could be called upon to "light up" the immediate battlefield at night or deliver protective "walls" of moving smoke to help conceal allied movements during the day. The crew actuated the M19 by dropping an armed projectile down the smoothbore muzzle (the M19 was a "muzzle loaded" weapon). The projectile's base would then contact the awaiting firing pin and enact the projectile's propellant, sending it across a pre-determined trajectory based on the elevation angle and traverse set by the mortar crew, eventually impacting in the target area. Muzzle velocity was rated at 550 feet per second while effective range was out to 5,870 feet (1,790 meters).
To help keep the system lightweight, a simplified spade baseplate was fitted as part of the M1 mount. This allowed the operating crew complete freedom when addressing elevation and traverse angles. While well-intentioned, this made the M19 inaccurate for the needs of experienced mortar crews and a general dislike of the new weapon was made known. Thusly, a more conventional mount - the M5 - was developed to compensate and help improve accuracy though at the expense of lesser range and additional weight. The elevation arc - when using the M5 mount - were set between +40 and +85 degrees while traverse was limited to 14 degrees.
Due to the inherent limitations with and without the M5 mount, the M19 was replaced by the longer-range M224 series mortar (this also replacing the aged M2 series) beginning in 1982 while stocks of M19s were exported to the armies of Belgium, Canada, Lithuania and Turkey. As of this writing, it is believed that the Canadian Army still makes use of the M19 mortar.
It is of note that the M19 did live a long enough life within the American inventory to see some use in both the Korean and the Vietnam wars by the Army and Marine Corps.