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Night Combat


Photograph of naval bombardment at night

U.S. Army. Via ibiblio.org

Night operations played an important role in the Pacific War. Forces that would have been at a fatal disadvantage operating in daylight were sometimes able to operate under cover of darkness. This was true on land, at sea, and in the air.

What distinguished night combat from day combat was, of course, reduced visibility. Human scotopic (low-light) vision depends on the rod cells in the retina of the eye, which are very sensitive to low light levels but have no color discrimination. Furthermore, the rod cells are connected into large clusters that further increase light sensitivity, but at the expense of reduced visual acuity. Thus, in very dim light, the human eye gives colorblind 20/200 vision at best. Rod cells respond slowly to changes in light level, which further increases their sensitivity, but at the expense of blurring any rapid motion.

It takes some time for the eye to adjust to low light. The pupil of the healthy eye expands to its maximum diameter in less than a second, but it takes much longer for the rod cells to build up sufficient light-sensitive pigment for maximum sensitivity. Some measure of scotopic vision is possible within 30 seconds, but full dark adaptation can take up to half an hour. Bright light rapidly destroys the light-sensitive pigment, which is a necessary biological adaptation for protecting the rods from bright light, but this means that lookouts exposed to bright flashes of light will lose their scotopic vision for a significant period of time afterwards. However, the pigment in rod cells is almost completely insensitive to red light. This means the eye is practically blind to dim red light, but it also allows observers to use red illumination without destroying their scotopic vision.

The light-sensitive pigment of rod cells is derived from Vitamin A, which means that persons lacking this vitamin in their diet suffer from night blindness. However, large doses of Vitamin A do nothing to improve night vision beyond normal human limits. While it is a myth that blue-eyed persons generally have better scotopic vision than brown-eyed persons, there is some genuine variability from individual to individual in quality of scotopic vision.

The only practical way to improve an individual's scotopic vision is to use artificial devices to increase the amount of light reaching the eye. During the Pacific War, electronics were not compact enough to permit practical use of active light amplification devices ("night vision") and artificial aids were limited to passive optical systems, such as large binoculars. It is not possible even in theory for a passive optical device to increase the surface brightness (light energy per square degree) entering the eye, but optical devices increased the apparent angular size of objects and thus made them easier to spot.

Reduced visibility under night conditions meant that night combat tended to occur at close quarters and was hampered by an inability to distinguish friend from foe. This was an invitation to lethal friendly fire incidents. However, it also increased the opportunity to achieve surprise. Many, if not most, night operations did not actually seek combat, but made use of night conditions to avoid combat and carry out movements that would have been spotted and opposed in daylight.

Night visibility was greatly affected by moonlight, which varied with the time of day and month and with weather conditions. A moonless night with cloud cover offered almost nothing for human vision to latch onto, and night operations were all but impossible. On the other hand, a clear night with a full moon is well within the range of mesopic vision, in which the cone cells of the eye begin to contribute to vision and bright colors begin to become visible. Military operations in bright moonlight were thus an intermediate case between dark night operations and daylight operations. 

Under conditions of severely restricted visibility, the other senses come into greater play. Many troops placed noisemakers in front of their positions to give away enemy infiltrators. For example, Marines at Guadalcanal attached empty tin cans containing a few pebbles to their barbed wire obstacles; these would rattle if a Japanese infiltrator disturbed the barbed wire. However, relying on hearing was problematic in the jungle, where the abundant animal life generated its own sounds. Many a rodent or land crab fell victim to a grenade lobbed by inexperienced troops. Marine veterans of Guadalcanal claimed that they could smell the body odor of Japanese troops at close range in the dark, and it seems likely that this worked both ways.

Radar promised to penetrate the dark of night and reveal enemy forces attempting movement, particularly at sea or in the air (though the best Allied microwave radars had the ability to detect vehicles on land by the end of the war.) However, effective use of radar required sophisticated command and control arrangements to replace the automatic signal processing of visual information in the brain, a fact that the major powers were generally slow to recognize until combat experience drove rapid improvement.

Night naval combat. Nighttime visual observations were limited by the very low contrast of ships against the horizon. This could be reduced almost to zero if the ships were in front of a land mass. Large warships were almost always equipped with a number of powerful searchlights, originally designed to spot torpedo boats in time to destroy them before they came within torpedo range, but these could also be used to spot larger warships or approaching aircraft. Of course, the use of searchlights gave away any hope of surprise and pinpointed the location of the ship for the enemy.

The Japanese Navy placed great emphasis on night operations in their tactical doctrine. The Navy expected to fight a Great Decisive Battle with any American fleet approaching Japan, and planned to reduce the Americans' likely numerical advantage in battleships by whittling down the approaching American battle line with night torpedo attacks. The Japanese took great pains to maximize the capabilities of their lookouts, who were carefully selected for their superior night vision, supplied with enormous pedestal-mounted binoculars, and trained to cover their eyes whenever their ships' guns were about to fire (as signaled by a double buzzer.) Japanese ships always fired their guns in salvo rather than continuous fire at night to ensure that lookouts could protect their night vision, and the Japanese put considerable effort into developing flashless powder that both protected their lookouts' night vision and made the flashes harder for an enemy to detect and get a fix on.

Japanese optics included binoculars with apertures as great as 21 cm (8.3"), but the most common was the Type 88 Model 1, adopted in 1932. These binoculars had apertures of 12 cm (4.7") and were of high optical quality.

To avoid giving away their positions with their own searchlights, the Japanese also developed effective star shells. The type adopted in 1935 was a parachute-suspended shell with a great illuminating radius. The 8" (203mm)  star shell had a candlepower of 1,700,000 candelas, while the 5" (152mm) version had a candlepower of 680,000 candelas and an effective range of perhaps 8000 meters (8700 yards). The American counterpart saw much less use, due to American reliance on radar, but was sometimes used in an amphibious support role to illuminate battlefields for ground forces. American 5" (127mm) star shells had a range of 12,000 yards (11,000m).

The U.S. Navy seems to have assumed that any major surface gunnery duel would take place in daylight, and their night lookouts were initially far less effective than their Japanese counterparts. American gunpowder was virtually smokeless, highly insensitive and gave very high performance, but it also gave an extremely bright flash. Lookouts were not trained to protect their vision when the guns fired at night, continuous fire was commonplace, and even the night lighting in prewar ships was a dark blue rather than the far more optimal red. Superiority in radar only slowly compensated for the Japanese advantage in night visual observation.

Notwithstanding the assumption that major gunnery duels would take place in daylight, the U.S. Navy had a well-developed doctrine for night combat by light forces that was not dissimilar to Japanese doctrine. Destroyers were to scout the enemy screen, firing star shell to reveal enemy screening ships without giving away their own positions. Cruisers would then destroy the illuminated enemy screeing ships with long-range gunfire, creating a breach in the enemy screen through which the destroyers would move to attack the core of the enemy formation.

The British had perhaps the only navy in the world that approached the skill of the Japanese in night combat. However, night engagements between the two navies were few in number. A pair of old British destroyers succeeded in penetrating a vastly superior Japanese screen off Endau in January 1942. and one managed to escape, but without infilcting any significant damage on the Japanese. The battle of Malacca Strait in May 1945 was a decisive British victory, costing the Japanese the heavy cruiser Haguro, but as the final surface engagement of the war, had no effect on its outcome.

Because limited visibility reduced combat ranges, night naval combat tended to be dominated by torpedo attacks, at which the Japanese with their "Long Lance" torpedo excelled. It took some time for the Allies to develop their own torpedo attack doctrine that took full advantage of their superior radar, but thereafter the Japanese lost their dominance of night naval actions.

Night aerial combat. Early in the war, there was no way for fighter aircraft to operate effectively at night. Fighters had almost no ability to spot enemy aircraft, even if ground-based radar was able to guide them to the general vicinity of enemy bombers, and most pilots lacked the training to safely land at night by instrument after completing their mission. A fighter that did somehow stumble across an enemy bomber was as likely to be surprised as to achieve surprise, particularly since the bomber had more than one lookout and they were not distracted by the need to watch flight instruments.

Under these conditions, it seemed that the bomber could attack with impunity. However, the cloak of darkness protecting the bomber also protected its targets. Night navigation was a very difficult task and raids early in the war were lucky if their bombs came within a mile of the target. Furthermore, ground antiaircraft guided by searchlights or radar became increasingly effective.

The Japanese nonetheless developed considerable skill at aerial torpedo attack at night. The attacking aircraft were usually long-range twin-engine bombers such as the G4M "Betty" rather than more conventional carrier torpedo aircraft. These long-range aircraft would painstakingly pinpoint Allied task forces, then brightly illuminate the target with lines of very bright floating flares, allowing the bombers to make their approach in the darkness. These tactics proved deadly at the Battle of Rennell Island, and were neutralized only with the advent of superior Allied night fighters.

The Allies made considerable progress in developing night fighters during the war. These were made possible by the development of airborne radar that could be carried in a two- or three-man aircraft and allow it to locate enemy bombers. These could then be destroyed, typically using oblique-firing fixed cannon that allowed the night fighter to approach its target from below and to the rear. The U.S. Navy tried a somewhat different approach beginning in late 1943. Night combat air patrols consisted of a radar-equipped Avenger accompanied by a pair of conventional Hellcats, with the Avenger acting as an airborne controller to direct its fighters onto the enemy. This required rather careful coordination, and naval ace "Butch" O'Hare was lost on such a patrol when he was caught in the crossfire between a "Betty" and his own lead Avenger. Later in the war, radar was developed that was small and simple enough to be operated from single-seat fighters. This allowed such fighters to operate effectively on their own.

Enterprise was specially modified to operate night air groups, with white "victory lights" on posts on either side of the flight deck to mark the first crash barrier and the standard red deck lights were adjusted to be visible earlier in the carrier approach and give the pilot better depth perception.

Allied bombers also acquired radar and an improved ability to attack at night. The "Black Cats" were BPY Catalinas so equipped and trained to attack Japanese surface forces at night. These slow, ungainly aircraft would have been sitting ducks for fighters in daylight but proved effective at hight. Conventional bombers also acquired radar, and the B-29 was equipped with a sophisticated radar from the start.

Night ground combat. The Japanese Army, like the Japanese Navy, emphasized night combat in its tactical doctrine. Most of the Japanese attacks during the Pacific War took place at night in order to neutralize Allied firepower and make the most of supposedly superior Japanese "fighting spirit."  Objectives were more limited than in a daylight attack, though the recommended depth of the final objectives was still an ambitious 1100 yards (1000 meters). The terrain features to be captured were carefully defined, and villages were to be avoided as too difficult to attack at night. The Japanese distinguished between a kishu, a night attack by surprise, and a kyoshu, a night attack by force. A kishu was essentially a bayonet charge without artillery preparation or small arms fire, to take maximum advantage of surprise, and it was to be used to seize the first objectives. The troops involved were frequently ordered to unload their rifles to ensure that an errant rifle discharge would not give away surprise. They also smeared their bayonets with mud to prevent them reflecting light, and tied cloth around their metal equipment to reduce noise. According to some oral accounts (Tamayama and Nunneley 200), even the use of grenades was avoided, since the fuses on Japanese grenades burned visibly. A kyoshu was a more systematic attack with full artillery and heavy weapons support, used against second objectives or when the enemy was thought to be expecting a night attack.

The Japanese also made frequent use of infiltrators and harrassing fire at night for its effect on the morale of Allied soldiers. Men are at their most psychologically vulnerable at night, and this multiplied the effect of harrassing activities. Japanese infiltrators were typically lightly equipped, often with just a few grenades and a close combat weapon, and could move very stealthily through jungle.

Allied soldiers, by contrast, generally attacked in daylight and stayed in their foxholes at night, assuming that anyone up and moving around was a Japanese infiltrator. If the Japanese staged a full-scale night attack, the Allied troops would reply with massed small arms fire and artillery, sometimes calling down the shells almost on top of their own positions in the belief that they would be much less vulnerable in their foxholes than the Japanese in the open. Night attacks were particularly vulnerable to artillery fire because of the tendency of troops to bunch up in the darkness. The Allied troops might also call for illuminating fire (very bright parachute flares fired from mortars and other artillery) to make the attacking Japanese more visible. At Bougainville, the perimeter fortifications included search lights and improvised illuminating grenades.

The fact that such attacks were almost always broken up, in spite of the emphasis on night attack in Japanese training, illustrates the difficulties of staging night attacks. Although darkness provided cover and increased the chances of surprise, it also meant that attacking troops easily became disoriented and lost. A successful night attack required thorough reconnaissance and a high degree of initiative among junior officers, but the Japanese often relied instead on shock and mass for success. This is particularly surprising given the Japanese skill at infiltration. However, the Japanese Army had had its eyes on mainland Asia during the development of its prewar doctrine, and night combat doctrine that proved inadequate in the jungle might have fared better in less terrible terrain.

British practice (and likely that of other armies as well) was to place pairs of infantrymen well in front of the main line of resistance in observation posts. These men were expected to let enemy patrols pass them, then signal their presence with a flare gun that also illuminated the infiltrating patrol. Other pairs of infantrymen stood watch just in front of the main line of resistance, and signaled the approach of the enemy by tugging on a log-line running back to the main position.

References

Bailey (2004)

Bergerud (1996)

Berman (2011)

Cannon (2015)

Crenshaw (1995)

Evans and Peattie (1997)

Fraser (2007)

Gailey (1991)

"Handbook on Japanese Military Forces" (1944-9-15; accessed 2011-11-24)

Hezlett (1975)

Sledge (1981)

Smith (2000)

Tamayama and Nunneley (2000)

Tillman (2012)


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