Artillery is the branch of the military that specializes in the use of long-range weapons to deliver fire against the enemy. During the Second World War, these weapons were mostly various kinds of tube artillery, though rockets became increasingly important as the war progressed. Tube artillery included mortars, howitzers, and guns of various calibres that fired explosive or chemical projectiles.
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Mortars are perhaps the oldest form of artillery, dating back to the very beginnings of the use of gunpowder in warfare. A mortar is little more than a hollow tube with a firing pin in its base, supported by a base plate and a bipod. Most fired an explosive shell with a propellant cartridge in its tail, which was dropped into the muzzle of the mortar to be set off by the firing pin. The tube was usually unrifled, and stability in flight was achieved by putting fins on the tail of the mortar shell. Mortars were fired at high angles, over 45 degrees, from positions very close to the front line. Thus, mortars were relatively easy to manufacture and transport, had a rapid response time, and could be fired over intervening obstacles. Their nonspinning, low-velocity shells were relatively quiet in flight, giving little warning. On the other hand, mortars have a relatively short range and only moderate accuracy.
The mortars used in the Second World War ranged in caliber from the 50mm German and Japanese models, which were little more than grenade launchers, to giant siege guns. However, the heaviest mortars regularly employed in the Pacific were about 120 mm in caliber. Only heavy mortars were still controlled by the artillery: Light and medium mortars, with calibers less than about 100mm, had become infantry weapons.
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Howitzers were
breech-loaded artillery pieces with rifled barrels characterized by a
short barrel and relatively large propellant charge. They fired a
relatively large shell at moderately high angles, though not as high as
mortars. Their range was sufficient that they could be deployed some
distance behind the front line. They were otherwise similar to guns.
Guns varied in caliber from
75mm on up. These fired an
explosive shell from a long rifled barrel at high velocity, giving them
considerable range and accuracy. The shells usually are fired at a low
angle of elevation and have a relatively flat trajectory.
Both howitzers and guns required large exposed crews and ammunition dumps that were vulnerable to counterfire. This meant that they were rarely positioned in the front line or immediately behind it. As a result, they could not respond as quickly to a call for fire as could mortars. On the other hand, their long range meant that a battery of many guns could cover a large region of the front, bringing down massed fire at the desired point.
Artillery rarely fired at a target they could see. Instead, they were directed onto their targets by a forward observer who communicated back the coordinates to be fired on and corrections to aim. Where there was time to prepare positions, the forward observers were often equipped with telephone lines back to the batteries. In mobile situations, or when telephone lines were destroyed by counterfire, the observers relied on radio equipment to communicate with the batteries.
The fire missions themselves could take several forms. Harrassing fire consists of an occasional shell fired in the general direction of the enemy, and its purpose is to keep the enemy from resting or moving about freely. Very few casualties are expected from harrassing fire, but the psychological effect can be quite significant, as American troops learned early in the Guadalcanal campaign. The Japanese had brought in a few large artillery pieces, but these were very short of ammunition and could engage in little but harrassing fire. The Americans nonetheless found the occasional potshots at Henderson Field highly aggravating and nicknamed the unseen Japanese gunner "Pistol Pete." Counterbattery fire was attempted along with ground attack missions by aircraft from the airfield. "Pistol Pete" would make his appearance from time to time through the remainder of the war.
Preparatory fire was intended to weaken enemy positions that were about to be attacked. The intensity of fire was sufficient to destroy communications lines, inflict casualties, and force the defenders to get under deep cover. Prolonged preparatory fire could destroy weaker field works and disrupt barbed wire barriers and minefields. Troops under prolonged artillery fire suffered from reduced reaction times and morale. However, a long preparatory barrage sacrificed surprise and often turned the target into a morass through which movement, particularly by vehicles, became very difficult. Preparatory barrages lasting days were not unknown in the First World War, but by the time of the Second World War, most preparatory fire was just long enough to force the defenders into cover and reduce their reaction time, after which the attackers attempted to move up before the defenders could recover. This required careful coordination, and many attacks failed, either because the effects of the preparatory fire had worn off by the time the attackers reached the enemy positions, or because the attackers were caught in their own barrage.
Defensive fire consisted of heavy barrages (often prearranged) into the staging areas from which an enemy attack was being organized. Because attacking troops had to mass and break cover to carry out the attack, well-timed defensive fire could be devastating and stop an attack cold. American artillery saved many an American position faced with a Japanese infantry charge, as at Bloody Ridge at Guadalcanal or on Saipan. In the latter case, the artillery fired directly on massed enemy troops at point-blank range before the attack was broken up.
Counterbattery fire was directed against enemy artillery positions, which were highly vulnerable if they could be accurately located and targeted. This proved difficult because of the natural cover in much of the Pacific and because the enemy batteries were usually well behind enemy lines. Air reconnaissance or infantry patrols occasionally pinpointed a battery, but much counterbattery fire was harrassing fire directed at the sound of the enemy guns. Radar revolutionized counterbattery fire in Europe, since the best microwave radars developed by the Allies were capable of tracking a shell in flight and projecting its trajectory back to the point of origin. It is unclear to what extent radar was used this way in the Pacific.
Covering fire was used to protect troops in the open from enemy small arms fire, by forcing the enemy to take cover. It could be used to assist an attack after the attacking troops made contact, or, when things went wrong, it could protect retreating troops. Covering fire required flexibility and was often best supplied by the infantry's own mortars.
The Japanese were handicapped by a relatively weak industrial base that made it difficult to equip their army with large numbers of guns and howitzers. However, the Japanese were fond of mortars, though most of these were smaller infantry mortars. Most infantry divisions had an artillery regiment equipped with 36 75mm howitzers or mountain guns. In a few of the better-equipped divisions, a third of these guns were replaced with 105mm howitzers. Independent mixed brigades typically had eight 75mm howitzers.
Japanese howitzers had a distinctly obsolete look to them, since most still used wooden-spoked wheels and were horse-drawn. The chief weapon was the 75mm Improved Type 38 howitzer, with a range of 12,400 yards and a maximum rate of fire of 10-12 rounds per minute. It was clearly an obsolescent weapon, and the Japanese began manufacturing the Type 95 prior to the war, which had some design improvements but only a small improvement in range. The Type 90 was a modern design with rubber tires intended for truck towing. Neither of the newer types were used in great numbers in the Pacific.
The 75mm Type 94 mountain gun could be broken down into eleven components that could be packed by six horses. Its range was only 9000 yards.
The 105mm Type 91 howitzer could fire to 11,500 yards at a maximum rate of 6-8 rounds per minute. However, it was not produced in sufficient numbers to equip most divisions. The much superior Type 92 gun, which could fire out to 20,000 yards, was supplied only to non-divisional artillery regiments. A few of these guns made it to Guadalcanal and were known as "Pistol Petes" for their harrassing fire. There was also a 105mm mountain howitzer that could fire out to only 6000 yards.
Larger nondivisional artillery pieces included 120mm, 150mm, 240mm and 305mm howitzers; the Type 89 150mm gun; and the Type 98 320mm spigot mortar.
The Japanese also developed infantry guns designed to be used close
to the front line. The Type 92 70mm infantry howitzer could fire an 8.3
pound (3.8 kilogram) shell to 3050 yards (2790 meters). It was most
typically used like a long-range mortar, but it could also be used in
the direct fire role, and shaped
charge shells were provided to allow it to be used in the antitank role. It appeared unreliable
and inefficient to Allied intelligence,
but remained in use throughout the war, and large numbers were captured
by the Chinese Communists
in Manchuria and employed in the
civil war.
The Type 41 75mm regimental gun was a very old design firing a 12.5
pound (5.67 kilogram) shell to 11,990 yards (10,960 meters) that was
widely used throughout the war as a direct-fire weapon. It was the
first Japanese weapon supplied with a shaped charge for antitank use.
U.S. artillery was modern, well-organized, and plentiful. A standard infantry division was equipped with an artillery regiment having 54 105mm howitzers and 12 155m howitzers. American communications were good, and American artillerists perfected the art of bringing every piece within range to bear on a single target. The ideal was the TOT or Time On Target attack, in which the more distant batteries fired first so that the shells from all batteries hit the target area at approximately the same time. When properly carried out, a TOT attack could be devastating, since a storm of shells arrived all at once with little warning.
The backbone of American artillery was the M2A1 105mm howitzer,
which could fire shells out to 12,205 yards at a sustained rate of fire
of 2 to 4 rounds per minute. This was backed up by the M1 155mm
howitzer, with a range of 16,000 yards and a sustained rate of fire of
2 rounds per minute.
A large proportion of the artillery of the U.S. Army was nondivisional. The backbone of the independent artillery regiments was the 155mm M1A1 Long Tom gun, which could fire out to 25,395 yards at a sustained rate of fire of a round per minute. It was paired with the 8" (203mm) howitzer, which could reach out to18,510 yards at a sustained rate of fire of a round every other minute. Both guns were so heavy that transport was a serious problem. Initially the guns were moved using civilian Mack 6x6 7.5-ton trucks, but by 1943 a purpose-build prime mover, the M4 HST, became available. Most of these heavy artillery pieces were controlled at the corps level.
The 240mm M1 Black Dragon howitzer was the heaviest American
artillery piece to see service in the Pacific. These massive pieces
were transported with the T16E1 prime mover, which used three pairs of
medium tank tracks. They were
emplaced with the 20-ton Laraine Crane
M2, a process requiring about two hours. However, the Black Dragon
could fire a 360lb (150kg) shell out to 25,225 yards at a rate of a
round every other minute. Though mostly seeing service in Europe, a
battery of Black Dragons participated in the fighting at Manila in early 1945.
A few batteries of 8" (203mm) M1 gun also saw service in the Philippines. This gun could fire shells out to 35,000 yards at a rate of a round per minute.
British and Australian infantry divisions were equipped with 54 to 72 of the 25-pounder gun. This was a versatile 87.6mm weapon with properties intermediate between guns and howitzers. It could fire a 25 lb (11.3 kg) shell out to 12,253 yards.
Nondivisional artillery consisted of 5.5", 6", and 7.2" howitzers.
References
The Pacific War Online Encyclopedia (c) 2007-2008 by Kent G. Budge. Index
