The Beginnings of ABM in World War II.

[MKSheppard]

In World War II, the British actually used their CHAIN HOME radar systems to detect incoming V-2s; they gave them about four minutes' worth of warning, and the British immediately began planning active defense against the V-2.

First proposal was made on 24 August 1944 by AA Command. Basically, they'd place a 40 kilometer wide barriage of gunfire in the path of the approaching V-2 with 320,000 rounds of shells per V-2. About 2% were expected to be duds; meaning that about 90 tons of explosive would be falling back down from the barriage; compared to the one ton warhead of the V-2. So this was of course not implemented.

By 19 December 1944; AA Command had refined their anti-V2 system quite a lot.

The new plan consisted of two modified GL radars at Aldeburgh and Foreness facing each other to triangulate the location of the V-2 as it passed between them. This combined with the information from the CHAIN HOME radar system on the V-2's launch point, allowed an accurate track to be constructed, enabling prediction of the future point of the V-2 at any time.

The track was then passed on to AA Command, and at a specified point in time, the AA guns were brought to bear at a fixed point in the air that the V-2 would have to pass through in order to strike it's predicted point of impact. 150 rounds of ammunition would have been fired into a 1,000 meter square at 20,000 feet. Detailed calculations were made and concluded that the chances of a successful intercept were 1 in 50.

By late March 1945, a lot of advances had been made in predicting the V-2s trajectory via obtaining three accurate point fixes. The first point, the location of launch, was obtained by a modified US SCR-584 set in Holland. The last two were obtained through modified GL Mk II sets in Aldeburgh, Southwold and Walmer through cross referencing.

The entire Greater London area was then divided into a series of 2.5 km grid squares, and gun firing tables were pre-computed for each grid to destroy a V-2 inbound for that grid. It was estimated that 60 to 500 rounds of ammunition would have to be fired to destroy each V-2, depending on where the impact point was in relation to the various gun sites. Actual trials of the radar tracking system successfully predicted with 81% accuracy the impact point of the V-2s in the predicted grid square; or in adjacent grid squares.

In the end; before AA Command could get permission from the War Cabinet to try out the plan; Montgomery's armies overran the areas of Holland where the V-2 attacks were being launched from.