The great gunnery revolution occurred between 1890 and 1945. During this period, paradigm shifts created the need for new inventions. The result was continual improvement in gunnery. A major thesis of this paper is that evolution of thought resulted in changes of technology and great increase in effective battle ranges.
The stunning improvement in gunnery over time can be seen the Table 1 below, by observing the increase in battle range with generally constant hit percentage.
|1898||U.S.A.||Spanish/Amer||2000 yds||2% (3)(4)||TBD1|
|1905||Japan||Russia-Japan||6500 yds||20% (3)||J. N. Westwood|
|1914||Germany||WWI Jutland||16000 yds||3.5%||Campbell|
|1943||U.S.A.||Guadalcanal||16000 yds yds||16% (2)||TBD3|
When nations of similar technical ability compete, similar technologies and capabilities result. This is certainly true for naval gunnery. The French invented the high velocity gun, but the British and Germans soon produced similar weapons. The British pioneered central fire control in 1910, but by 1914 the Germans possessed less sophisticated system but with similar capability. In the story of gunnery evolution, the original creator of an idea is often unclear. Military secrecy and loss of records over the years clouds the detail. As a result, the account that follows necessarily relies on most available data which is often British. Despite such reliance, ample evidence exists of roughly parallel developments in France, Germany, America and many other countries.
The Gunnery Problem:
Naval gunnery is unlike shooting a bb gun at an arcade, where hit after hit can be achieved by a skilled shooter. Naval gunnery is more comparable to a boy standing by a lake who throws rocks at a distant turtle. The splash of the first rock is short and the boy throws harder. Soon, the boy "finds the range"; but even then, he cannot repeatedly hit the target. The arc of the throw and variations of wind frustrate absolute accuracy. The best he can achieve is to drop rocks in a cluster, about the turtle. After "the range is found", some statistical percentage will hit. Naval gunnery is much the same.
For boy and naval gunnery alike, two parameters describe capability.
Birth of the High Velocity Gun:
American civil war photos show thick, stubby gun barrels of the period. Photos of contemporary European artillery look much the same. Fast burning gun powder generated tremendous and instantaneous pressure within the gun. Such great pressures necessitated thick, stubby gun tubes.
During the 1870's, French Military Engineers changed all that. They invented slow burning powder which gradually expanded as projectiles accelerated down long and slender gun barrels. The marriage of slow burning powder and long gun barrels resulted in greatly increased shell velocities (2500 ft/sec).
Invention of slow burning powder stopped the progression or larger and larger guns. The twin French inventions (slow powder and long barrels) enabled development of small, quick firing guns capable of "poking holes" through thick armor. The French (and other nations) married this technology with the breach loading (not down the barrel) gun to achieve high rates of effective fire.
Major naval powers were quick to follow the French (7). Britain developed the "wire wound gun" while Germany used shrink fit tube design. Other nations (including the U.S.) purchased gun technology from France, Britain or Germany.
Quick Firing Guns vs. Big Guns:
By 1890, technically advanced navies (France, US, Germany, UK, Russia, Austria & Japan) employed high velocity, breach loading guns. Naval experts around the world understood that big guns were very heavy. The choice was to employ a few big guns, or many smaller ones. From 1890 until 1906, gunnery experts debated the relative effectiveness of a few big, powerful guns (e.g. 12 inch diameter bore) vs. many smaller quick firing guns (e.g. 6 inch to 8 inch diameter bore). Proponents of the quick firing guns argued that the smaller gun would smother the target before the larger gun made a single hit.
The inability to quantify the benefits of small, medium or large guns resulted in battleships of mixed battery. These ships often carried a mix of 12 inch, 8 inch and 6 inch guns to engage other battleships. In addition, they typically carried a battery of 3 inch guns for use against torpedo boats. These "mixed battery" battleships made their debut in the Spanish American War and again in the 1904 Russo Japanese War.
The twin gunnery problems are 1) time to find the range and 2) percent hits afterwards. During the 1905 Battle of Tsushima, the victorious Japanese fleet required 15 minutes to "find the range". We might wonder why it took so long.
Returning to the "turtle analogy", a single boy throwing rocks at a turtle quickly finds the range. But when five boys all throw rocks at the same turtle, the problem becomes far more difficult. Each boy becomes confused regarding which splash was his. Often as not, he observes the fall of someone else's rock, and wrongly adjusts his next throw.
At the Battle of Tsushima, likely 20 big guns all fired at the same target. The splashes of 6 to 12 inch projectiles were confused, rendering accurate observation and correction by each gunner impossible. In 1906, British Navy took a bold step to address this problem. HMS Dreadnought was launched. Unlike its predecessors, Dreadnought was armed with 10, 12 inch guns, mounted in twin turrets. There simply were no 8 inch or 6 inch guns to cause confusion. Soon after, all major powers began building "all big gun" ships of their own. The Dreadnought age was born; but, another 6 years elapsed before the invention of central fire control delivered the full benefits of the "all big gun ship".
Invention of Central Fire Control:
The "all big gun" ship greatly reduced the confusion that resulted from splashes of multiple calibers of gun firing concurrently. (Confusion was still possible between the splashes of different 12 inch guns). In 1910, the British Navy carried out secret trials between two identical ships, one using traditional single turret firing and the other equipped with the newly invented central fire control system. The centrally controlled firing system, aimed, elevated and fired all big guns simultaneously. The 8 to 10 projectiles landed simultaneously in a pattern before, behind or around the target. The multiple splashes were easy to observe and all guns were corrected simultaneously. Central fire control ensured that gunnery corrections were correlated to correct observation of fall of shot thus minimizing time to "find the range".
Shortly after its introduction, a gunnery competition was held between two identical battleships (Thunderer & Conqueror). One was equipped with the new, central fire control system and the other used the traditional turret by turret command of fire.
Naval officers carefully observed the fall of shot to determine which method was more effective (in terms of finding the range quickly). Detailed analysis confirmed the obvious, that the central fire control system was far more effective than turret by turret fire control. (see Peter Padfield Guns at Sea for details).
The Central Fire Control System offered several advantages over the traditional system. First, all the guns on the ship were fired together thus resulting in a statistical pattern of splashes fitting one of three descriptions:
Invention of Fire Control Computers:
By World War I, battle ranges were such that shell flight time was approximately 30 seconds. During 30 seconds, a battleship cruising at 21 kts moved forward 300 yards. A perfectly aimed shell fired at the ship would thus fall harmlessly behind by the time it arrived. Simple math thus dictated that gunnery systems be developed that would enable shooting at the target's future location.
Just prior to WWI, major powers developed mechanical Fire Control Computers which integrated with Central Fire Control Systems to properly adjust the aiming point. The following elements were integrated into an effective system.
By WWI, Britain, Germany, the U.S. (and likely all other major powers) employed central fire control systems augmented by fire control computers. As a result, WWI naval battles were fought at ranges of 10,000 to 20,000 yards. At those ranges, 3% to 4% hits were achieved despite bad North Sea visibility with 11 inch to 15 inch guns.
While such percentages might appear low, the effect of such gunnery was devastating. During the Battle of Jutland, several British Battle Cruisers were blown apart when German shells pierced British magazines. German ships also suffered with Battlecruiser Lutzow sunk after 24 large caliber hits. Other German had barely a gun turret functional by the end of the battle (e.g. Von der Tann).
Between the Wars:
During the period between WWI and WWII, navies continued to develop more effective technologies. Reports of U.S. Naval practice during 1930s suggests percentage hits expected during battle should greatly exceed the 3% to 4% achieved in the North Sea during WWI. (see Warship International, W. J. Jurens, the Evolution of Battleship Gunnery in the U.S. Navy, 1920-1945). During the 1930-31 practice, three battleships fired 56 shots each (7 salvos) at 12800 yards range. The target was Battleship representative in terms of length and height. "West Virginia would have gotten five hits, Maryland six, and Colorado only one." Assuming such performance typical, 7% hits was achieved during the opening salvos of a mach battle. Records from both the British 5th Battle Squadron at Jutland and American interwar practice suggests about 4 salvos are required to "get the range" and "bracket" an enemy target. From this, we conclude that 3 or 4 salvos were simply thrown away and the long term interwar war hit percentage for American Battleships should be about 14%.
Rates of Fire:
The rate of firing for Battleship main armament increased from 1900 reaching its maximum about1930. For the Russo-Japanese war period (1904-05), Janes Book of Fighting Ships reports normal rate of fire for Russian battleships as one every 3 minutes. It appears the Japanese long term firing rate was similar in 1905. Jurens provides information for a later period. "In 1919, battleship main batteries averaged about 1.9 shots per gun per minutes. By 1930 the rate had risen to about 2.5 (but never got much higher than this).
Radar Fire Control:
During WWII, both the German Bismarck and U.S. battleships were equipped with Radar Fire Control. For the U.S., its effectiveness was such that even during daytime, it was used in preference to optical fire control. During the night actions at Guadalcanal, an American Battleship using Radar achieved 9 hits on a Japanese target after 56 rounds fired. Once again, the long term hit percentage would have been much higher if firing had been prolonged or if "ranging shots" are discounted.
From 1890 through 1945 a continuous stream of technological improvements increased battleship big gun effectiveness in terms of:
Prior to 1906, high rates of fire for the medium gun (6 inch to 8 inch) enabled them to compete with big naval guns (11 inch to 12 inch in that period). From 1906 to 1914, the emergence of Central Fire Control and Fire Control Computers ushered in the period of the Big Gun, a period when destructive power and accuracy of the big gun totally dominated naval warfare.
Battle ranges increased as percentage hits grew throughout the period. In 1898, 2% hits was achieved by the Americans in the Spanish American War at ranges of approximately 2000 yards. By 1905, the Japanese achieved 20% hits at battle ranges of 6500 yards in the Russo-Japanese War. By World War I, 3% to 4% was achievable under the worst sea conditions at 14000 yards range. During the interwar years, 15% hits at 15000 yards was a realistic battle expectation using optical fire control.
While such hit percentages may seem low, the enormous destructive power of each hit deemed it sufficient. Lutzow was sunk by 24 hits. Kirishima was effectively destroyed by 9 hits. Battlecruiser Hood was blown up after only a few hits. Such observations explain why the Battleship reined supreme for 50 years.Notes:
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Paul F. Watson