I cannot speak too extensively on what other nations did, but I can offer insight into how field artillery in the US Army conducted fire during the Second World War.

In the aftermath of the First World War the US Army conducted a rigorous self-examination meant to identify what it had done right and wrong in 1917-18. One key takeaway concerning the field artillery was that while it had been perfectly capable of supporting the infantry through well-planned fires it had failed to achieve the same effectiveness when it came to attacking targets of opportunity. As a result, during the Interwar Years a satisfactory method of fire control was sought that would allow for rapid shifting of fires about the battlefield. In 1929 a British field artillery officer, Lt. Col. Neil Fraser-Tytler, published a book detailing his experiences in the First World War. Fraser-Tytler had been a battery commander during the war, and, disgruntled with the monotony and ineffectiveness of conducting unobserved indirect fire, had begun sneaking into No-Man’s Land after dark with a telephone. Once he had reached a suitable OP, he would register his battery on various targets by firing only one gun and adjusting that fire onto the target. Once a target had been registered the battery recorded the corrected firing data and passed it along to battalion headquarters for dissemination to the rest of the unit. The system was not quite groundbreaking- indeed, it was simply a method of conducting observed indirect fire- but it served to inspire Major Carlos Brewer, Director of the Gunnery Department at the Field Artillery School, and by 1931 he and his instructors had developed a graphical firing chart drawn to fit the battery positions of the battalion and a battalion base point, the latter being a common reference point identified by a forward observer (FO) that each battery registered upon. With the real locations of each battery and the base point known, targets were identified relative to the base point through a request such as: “enemy strong point, reference point 600 left, 400 short.” This allowed each battery to quickly compute firing data by modifying the data it had computed through registration, in this case specifically adjusting it to hit a target 600 yards to the left and 400 yards short of the base point. Major Orlando Ward, Brewer’s successor, refined the system between 1932 and 1934 by transferring the responsibility of computing firing data from the FO to a group of personnel at the battalion level, called the fire direction center (FDC). He also transferred responsibility for directing fire, i.e. deciding which targets to fire upon and how to do so, from the battery commander to the battalion commander, and oversaw the adoption of radios, which considerably improved the reliability of communication between the FO and FDC. The new system was very fast- during one demonstration in 1933, the battalion massed fire (directed the fire of all of its batteries onto one target) on the target within 8 minutes- and allowed the battalion to mass fire using information provided by only one FO. Such a feat had previously been impossible, as targets had been identified relative to terrain features and a battalion shoot was only possible provided an FO from each battery could see it.

Despite proving itself as successful in multiple demonstrations in the 1930’s, the Field Artillery School’s new system was not well received. Institutional conservatism aimed at preserving the authority of the battery commander and simple refusal to believe that the system worked prevented its implementation until 1941, by which point it had been improved upon further by another Director of the Gunnery Department, Lt. Col. H.L.C. Jones. Jones gave the battery commander the job of directing fire in fast-moving situations, with battalion taking over once things had settled down. He enlarged the FDC and made the graphical firing chart the one-stop-shop for all computing and plotting, whether the battalion was delivering observed or unobserved fire, and improved the responsiveness of the system through the adoption of a graphic firing table that allowed for rapid computation of firing data. Finally, he adapted the system to mass an entire division’s artillery by registering one gun from each battalion on a division check point. Demonstrations for the Army Chief of Staff, General George C. Marshall, and Major General Robert Danford, Chief of Field Artillery, in April and October 1941 convinced both of the system’s merits, and it was adopted immediately. The system was then further improved (rather drastically) in June of 1942. As early as 1935 field artillery officers had advocated placing artillerists in aircraft to obtain the most effective use of aerial observation, but it was not until 1941 that the concept gained real traction. In May of that year a Field Artillery School committee recommended that observation aircraft be made organic to FA units, citing the increased mobility of enemy forces on the modern battlefield and the resultant diminishing returns of terrestrial observation as their cause. Following experimentation with Air Corps-provided air OP’s during the 1941 maneuvers, the Field Artillery Branch maintained its position, pointing out that under such an arrangement the availability of air OP’s was not guaranteed and that interservice cooperation in conducting effective fires was bulky. The branch was permitted to conduct further testing in the spring of 1942, during which it successfully proved its case, and on 6 June 1942 every field artillery battalion, field artillery group, and artillery headquarters at division and corps level received organic aerial observation in the form of two light observation aircraft, two pilots, and one mechanic.

With the addition of observation aircraft to field artillery unit TO&E’s the American fire direction system was complete. The graphical firing chart allowed for the registration of base/check points at ANY level of command and the graphical firing table allowed for such rapid computation of firing data that the only limitations on massing fire were range and ammunition, and the heavy American reliance on artillery as a sledgehammer reflects that. The massing of up to seven battalions through a single FDC, adjusted by a single FO, became routine, and time-on-target (TOT) concentrations, in which multiple battalions are massed in such a fashion so that all rounds impact simultaneously, became a favorite tactic. Massing the artillery of an entire corps became a regular occurrence during the North African and Italian campaigns, and its effect was awesome. On one such occasion, a German tank-infantry battlegroup was spotted by a 45th Division air OP as it formed up to assault division positions within the Anzio beachhead. Directed by the aerial FO, VI Corps artillery executed a bingo, massing the fire of 224 British and American guns in 12 minutes to obliterate the enemy formation before shifting fire to four other targets in the next 50 minutes. The Normandy campaign saw even greater concentrations employed, as inearly July 1944, for example, an attack on the village of Sainteny by a single regiment of the 83d Division was supported by the fire of a whopping 19 battalions, including the divisional artillery of the 83d, 9th, and 90th Divisions and corps artillery from both VII and VIII Corps.

While it is a good story to tell, I am afraid that it would be incorrect to say that the Finns were the only ones capable of massing the fire of 256 guns; the US Army massed the fire of many battalions very well, with exceptional speed, and did it very often. In terms of size, however, a 256-gun concentration massed on a single point is certainly in the running for the record for that particular category; unless the US or the Soviets beat it, and to my knowledge the fire direction systems of the latter were not as efficient. The only US shoot around that size would be that conducted at Sainteny or a second one conducted by VII Corps that I believe was purported as involving 21 or 25 battalions, which if the former is just under 256 guns providing each battalion is staffed by 12 guns (not all were; US Armored FA battalions contained 18 105mm M7 HMC’s, and these were present mostly in armored divisions and at the corps and group level) with the latter being greater. If you’re very curious about that I can confirm later, I am at work and can’t find the reference in the Green Books and do not have access to sources at home that I know for a fact reference it.