M12 155mm Self-Propelled Howitzer
Early in the World War II, the Ordnance Department developed the 155mm Gun Motor Carriage, M12, using the World War French type 155m GPF, which had a maximum range of 20,100 yards, on an M3 Stuart tank chassis.. One hundred of these were manufactured but there were no immediate requirements. With a crew of six, it was adopted in 1941 and proved very effective in the European Theater during World War II. It was capable of a maximum range of 21,982 yards. Experience in France showed the great value of highly mobile self-propelled artillery of this size, and urgent requirements were then submitted for the improved type standardized as the 155mm Gun Motor Carriage, M40 (T83). The M40 mounted the 155m Gun, Ml, which had a maximum range of 26,715-yards. The older M12 fired the first shot into Germany and the new M40 fired the first shot into Cologne. Also standardized was the 155m Howitzer Motor Carriage, M41, (T64E1). These weapons, which were mounted on medium tank chassis, demonstrate how successfully large weapons can be mounted on mobile ohassis to meet the specific needs of the using services.
The introduction of self-propelled artillery represented improvisation at its best. After expressing little interest with this form of field artillery for two decades and even opposing it, the War Department and field artillery officers abruptly changed their position after war in Europe had broken out. To stay abreast of the German juggernaut, they decided to obtain self-propelled artillery as soon as possible. Without the benefit of a solid research and development program, the Ordnance Department did nothing more than weld a M2 105-mm. howitzer to a medium tank chassis and send the weapon to the field.
The memory of the French 155-mm gun's uncanny accuracy, long range, and destructive prowess was still fresh in the minds of cannoneers when they were queried by the Westervelt Board just months after the Armistice. This group of ordnance and artillery officers had been convened to canvas its own and foreign artillerymen as to the relative merits of different cannon, as well as what they envisioned would be most desirable on any future battlefield. One of the Board's recommendations, submitted on 23 May 1919, called for a new improved 155-mm gun, with the extra proviso that a self-propelled version also be developed.
The goal of a self-propelled 155-mm gun, first articulated by the Westervelt Board in May 1919, came to a sudden halt in 1922 when the United States ceased its experiments. The objection that the entire weapon system would become immobilized once the engine in the carriage failed seemed to demonstrate at that point in time that tractor-drawn artillery was more dependable in combat. As a result, the very promising beginnings were destined to remain dormant for nearly two decades.
But the dream did not die, at least for ordnance experts. As early as June 1941, the Chief of Ordnance recommended the development of a 155-mm gun mounted on a modified M3 tank chassis. The skilled craftsmen of Rock Island Arsenal, once given the go-ahead, promptly fabricated a pilot model, which was tested at Aberdeen Proving Ground in February 1942. Designated the T6 GMC, it consisted of an M1918 155-mm gun (an aging veteran of World War I) emplaced on a mobile tank chassis. The Army Ground Forces, however, initially refused to consider this innovation, primarily because they could not see a need for such a weapon.
The Ordnance Department, however, still firmly convinced of the value of the self-propelled 155-mm gun, ordered 50 to be produced in March 1942. Converting to self-propelled and towed artillery opened a new era. With support from the field artillery, the War Department started arming the division with the towed (also horse-drawn) M1897 75-mm. gun, the towed M1916A1 75-mm. gun, the towed M1917Al 75-mm. gun, the towed M2 75-mm. gun, the towed M2 105-mm. howitzer, the self-propelled M7 105-mm. howitzer, and the towed M1918 155-mm. howitzer during 1942. Simultaneously, the War Department took steps to equip the corps with the towed M1 155-mm. gun, the towed M1 8-inch howitzer, and the towed M1918A 240-mm. howitzer. With the introduction of totally new field pieces to replace World War I guns and howitzers, the field artillery acquired the speed and mobility required to keep up with mobile armored and mechanized units being formed in the Army.
By late 1942 a new family of field artillery weapons existed. M2 105-mm. howitzers, self-propelled M7 105-mm howitzers, MI 4.5-inch guns, Ml 155-mm. guns, self-propelled M12 155-mm. guns, M1 8-inch howitzers, and towed M2 8-inch guns began to dominate the field artillery. These weapons had greater ranges than World War I artillery and even modernized World War I pieces. They fired high-explosive shell, chemical shell, steel shrapnel, and shot to pierce armor. To eliminate the necessity of carrying several kinds of fuses, field artillerymen detonated their ammunition with combination superquick-delay action fuses that could be set at the time of firing.
Despite additional objections, the new weapon system was standardized as the M12 and, production of an additional 100 was completed in March 1943. Once fielded, these pieces were used for artillery training in the United States. By December 1943, however, when the plans for the invasion of "Festung Europa" were being finalized, the decision was made to overhaul 74 of the M12s for possible use in overseas combat.
The Americans hit the beaches of Normandy on 6 June 1944. Examining the impact of self-propelled field pieces, the First US Army candidly admitted that attaching them to the assaulting parties greatly expedited establishment of a fire base during the initial stages of the landing. The Americans slugged their way through the hedgerows, which were earthen dikes about four feet in height and covered with tangled hedges, bushes, and even trees. The hedgerows hampered mobility and handicapped ground observation because they restricted visibility to one to two pastures at a time. Lieutenant Colonel Lewis R. Soffer wrote that his battalion could not use the mobility of its self-propelled M12 155-mm. guns, which had just been adopted, effectively in hedgerow country because the guns had to fight their way from field to field or move single file down the sunken lanes. The field artillery generally depended on organic air observation to adjust fire, and in some instances it furnished the only observed fire.
One of the first units to be furnished the M12 was the 991st Field Artillery Battalion, a former New York National Guard unit. Crews trained for 15 months with this new weapon—a 155-mm gun of World War I vintage mounted on the M4 tank chassis that had been stripped of armor and a spade added to absorb the force of recoil. As could be expected, crews encountered the normal difficulties of adjusting to a new artillery piece.
Typical American improvision and persistence however resolved their problems. By the time the 991st FA Battalion landed on Omaha Beach at Normandy on 11 July 1944, its crews and M12s were performing at peak efficiency. Since the M12 was capable of churning across terrain at 35 miles per hour, road marches of 200 miles per day were considered the norm, not the exception.
During the battle of Normandy, the M12s of the 991st FA Battalion were attached to the corps of the US First Army and were utilized primarily to deliver supporting fire. Following its attachment to the 3d Armored ("Spearhead") Division on 12 August, the 991st abandoned its static role for one of movement in the Battle of the Falaise-Argentan Gap. During this period, the M12s fired most of their missions against enemy flak batteries, field batteries, and deep interdiction targets, all in accordance with accepted field artillery doctrine for medium and heavy artillery. The heaviest day's shooting came on 17 August, when the M12s hurled 1,073 rounds on German Panzer tanks.
After the closing of the gap at Putanges, the M12 unit joined in pursuit of the retreating Wehrmacht. As the only artillery heavier than the ubiquitous 105-mm howitzers attached to the fast-moving 3d Armored Division, the 991st FA Battalion was the only unit available for deep counterbattery, long range targets of opportunity, interdiction, and covering fire during the emplacement of light artillery batteries.
Despite the speed of the advance across France, coupled with frequent displacements, the French GPF tubes of the M12s "again proved, as in the last war, that they could speak with authority on French soil." The rapid pursuit, however, permitted enemy units to infiltrate between the 3d Armored Division spearhead and the 991st FA Battalion and, for one 24-hour period, these fast-moving artillery units became virtually isolated from the rest of the corps and army.
As a result, the M12 battalion had to fight several infantry actions. The sharpest one came between 2 and 4 September 1944, when the 991st FA Battalion, aided only by headquarters troops of the armored division, fought off the remnants of the German 348th Infantry Division in the vicinity of Quevy-le-Grand. Its fire proved very effective on tanks, half-tracks, trucks, and personnel. In all, the M12 battalion took 500 prisoners. When the infantry arrived to take over, the 3d Armored Division roared off again, this time straight eastward toward Germany, with the self-propelled Long Toms following close behind.
To the M12 battalion went the honor of being the first Allied artillery unit, from the West, to unleash its deadly barrages on German soil. The target was a key road junction near Bildchen, a small town southwest of Aachen, at a range of 19,800 yards. The Long Toms of the 991st FA Battalion spoke authoritatively at precisely 1721 hours on 10 September 1944. This fire, according to the air observer overhead, proved "effective".
As the VII Corps assaulted the Siegfried Line south and southeast of Aachen, the batteries of the 991st FA Battalion assisted the combined tank/infantry effort to penetrate this strongly fortified line by destroying concrete pillboxes by direct laying. Battery A remained attached to the 3d Armored Division, while Battery B worked with the 9th Infantry Division in and around the Huertgen Forest. Battery C aided the 1st Infantry Division to first isolate Aachen and then speed the city's reduction by providing direct fire support to the infantry which was fighting street by street.
When the last great death gasp of the Third Reich on the western front erupted into the Battle of the Bulge, the fast-moving M12s fought first in defensive actions and then took the offensive with the First Army. Next, in January 1945, the 991st provided necessary fire support to assist the 1st Infantry Division to smash through the Siegfried Line southeast of Monschau and, after shifting to the north, supported the crossing of the Roer River, the drive to the Rhine River, and the capture of Cologne.
Next, the batteries of the M12 battalion, now attached to the Seventh Army's divisions, lent the weight of their awesome Long Toms to drive again through the Siegfried Line for the third, and last, time. Once the Seventh Army secured its Rhine River crossing at Worms, the 991st was shifted back to the 3d Armored Division and had to motor march 400 miles to rejoin this fast-moving "Spearhead."
The dictates of war had led the M12 battalion from the beaches of Normandy to the plains of Saxony, a mere 60 miles from Berlin. During this entire period, the 991st FA Battalion engaged in combat (except for one week of refitting in January 1945) until withdrawn from action at Dessau on the Elbe River on 25 April 1945. The battalion had worked with six US Army corps and was attached — a least components—to 13 divisions. From 11 July 1944 to 25 April 1945, the Long Toms of the 991st FA Battalion fired a total of 48,937 rounds.
In recognition of the self-propelled Long Tom's invaluable contribution to final victory, the cannoneers serving them received a Distinguished Service Cross (posthumously), 2 Silver Stars, 85 Bronze Stars, 7 Air Medals, and 14 Bronze Oak Leaf Clusters to the Air Medal.
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