Lets talk about just how far fleet air defence advanced during Second World War. Mostly because it's interesting, but also because some of the lessons learned by our predecessors might just remain relevant today...
This is, broadly, what a destroyer of the inter-war period looked like. This is HMS Walpole, a W-class destroyer commissioned by the RN in 1918.
Her air defence outfit at the outbreak of war in 1939 consisted of 2 manually sighted quad 40mm pom-pom mounts.
Her air defence outfit at the outbreak of war in 1939 consisted of 2 manually sighted quad 40mm pom-pom mounts.
And this is what the destroyer had developed into by 1945. Pictured below is the USS De Haven, an Allen M. Sumner class destroyer commissioned in 1944.
Her outfit consists of six radar-laid 5" dual purpose and 12 40mm Bofors guns plus 11 manually sighted 20mm Oerlikon cannons.
Her outfit consists of six radar-laid 5" dual purpose and 12 40mm Bofors guns plus 11 manually sighted 20mm Oerlikon cannons.
Not only did the platforms improve by orders of magnitude, the layered fleet air defence 'system of systems' became so potent from 1943-45 that traditional modes of air attack were abandoned by the Japanese in the Pacific. The losses of pilots and aircraft became unsustainable.
That layered system began with the outermost protective element, consisting of early warning provided by patrolling aircraft and later radar systems. British methods of fighter control using radar were honed in combat in the Mediterranean theatre with the Fairey Fulmar aircraft.
By 1944 the US Navy could rapidly detect, intercept and break up large and repeated air attacks. Inflicting massive losses in the process. At the battle of the Philippine Sea it is estimated the Japanese lost over 500 aircraft in exchange for just over 100 US machines.
At the same time the other defensive layers were also making vast strides.
The introduction of the proximity fuse for large anti-aircraft shells, including the US Navy's 5" AA shell, made them orders of magnitude more dangerous for attacking aircraft.
The introduction of the proximity fuse for large anti-aircraft shells, including the US Navy's 5" AA shell, made them orders of magnitude more dangerous for attacking aircraft.
Prior to the introduction of the "VT" (proximity) fuse, defensive fire from large anti aircraft artillery pieces relied upon mechanical fuses which set the shell to explode a specific time after it had been fired. In theory creating a wall of bursting shells and shrapnel.
Any attacking aircraft would have to fly through this zone, risking damage or destruction. In practice the destructive potential was limited. Once an aircraft got through the protective screen of shell bursts the effect of the heavy guns became negligible.
Proximity fusing allowed shells to be fired at the aircraft itself, bursting in the vicinity of it with much improved chances of causing damage.
When combined with large numbers of radar laid guns on high angle mounts this combination became extremely lethal.
When combined with large numbers of radar laid guns on high angle mounts this combination became extremely lethal.
The earlier barrage concept did, however, enjoy some notable success when employed with specialist platforms.
The US Navy's Atlanta class anti-aircraft cruisers were built around their extensive 5" dual purpose armament, mounting sixteen radar-laid 5" guns.
The US Navy's Atlanta class anti-aircraft cruisers were built around their extensive 5" dual purpose armament, mounting sixteen radar-laid 5" guns.
These ships could lay down a continuous (due to their many rapid firing 5" guns), dense and effective blanket of anti-aircraft fire.
A similar concept was also applied with the later Worcester class, with its twelve dual purpose radar directed 6" guns in high angle mounts.
A similar concept was also applied with the later Worcester class, with its twelve dual purpose radar directed 6" guns in high angle mounts.
The introduction and fitting of high angle mounts were a critical step which enabled escorts to defend themselves. Pictured is a typical first world war naval artillery piece, which still equipped many destroyers at the opening of WW2. It cannot elevate to engage aircraft.
Dual purpose guns, for use against both surface ships and aircraft had been available well before the outbreak of war. However, budgetary pressures and treaty limitations often meant that older ships were not replaced, nor new guns retrofitted.
When large numbers of the later generation of radar-laid high angle dual purpose guns, epitomised by the US Navy's Mk.38 5" gun, began to come on-stream there was a real step change in the defensive capabilities of individual surface units.
These gun systems were increasingly laid onto their targets, as the war went on, by radar directors like the US Mk.37 shown below.
These fed into mechanical or electromechanical fire control computers such as the US Mk.1 fire control computer, or the British HACS system.
These fed into mechanical or electromechanical fire control computers such as the US Mk.1 fire control computer, or the British HACS system.
The system of systems built by the US Navy, and to a lesser extent also by the Royal Navy, became so effective that it drove radical tactical innovation on the part of the enemy. The Japanese "Kamikaze" tactics of 1944-45 were not adopted because the Japanese were mad fanatics.
"Kamikaze" tactics were employed because 'conventional' attacks by massed air formations no longer worked. What the Japanese did instead was to develop a means of overwhelming the capacity of the US fighter controllers, Kamikaze attacks were conducted using lots of small groups
of aircraft, mixing conventional strike aircraft with suicide planes. By dispersing their forces and attacking unpredictably from many directions the Japanese could create more targets than the carriers' CAP and fighter controllers could handle. Some would inevitably get through.
Ultimately tactical counters to Kamikaze were developed, but it demonstrated that even a powerful and effective defensive system can be compromised without the need for equivalent technical development by the enemy.
Tactics were always as important as equipment.
Tactics were always as important as equipment.
By the end of the war naval surface forces had convincing answers to the problem of air attack. To the extent that even sustained large-scale attacks could be beaten off with limited losses.
This was down to a ruthless and continual process of technical and tactical improvement.
This was down to a ruthless and continual process of technical and tactical improvement.
Interestingly the Japanese developed the Type 3 "San Shiki" an 18.1" anti aircraft incendiary shell that could be fired from the main guns of a Yamato class battleship.
It wasn't very effective.
Engaging Strategy, out.
It wasn't very effective.
Engaging Strategy, out.
