Despite the fact that the first German magnetic mine unit was ready for operational in 1942, at the outbreak of the war in September 1939, insufficient stocks of magnetic mines were on hand to wage an all-out and effective mining campaign against England and her Allies. This shortage existed because the war came at a time when the Navy was still engaged in improving existing operational models and had not, as yet, gone into mass production. The existing stocks of magnetic mines were very small. They consisted of approximately six hundred LMA's and LMB's and several hundred RMA's and RMB's.

The German technical development of mine firing system fall into three stages. The first, the period from October 1939 to the Summer of 1941, was one of significant inno-vations. It saw the introduction of the magnetic mine with its successive modifications, followed by the rush development of the audic frequency acoustic and the combined magnetic-acoustic mines.

The German Navy expected the magnetic mine to suffice for the war, but within a year the British were applying successful countermeasures. The Navy placed the blame for this upon the Luftwaffe, which in 1939 laid the mines in the Thames estuary before enough were available for a heavy attack. The Navy felt that these were far more likely to be recovered than ship-laid or submarine-laid mines, which might safely be laid in small numbers.

Even before the British negated the effect of the magnetic mine, the German Navy began the rush development of the audio frequency acoustic and combined magnetic-acoustic mines. As a result, they were actually producing acoustic mines in small num-bers within three months after the out-break of the war. Quickly they overcame the operational limiations of the first models, and proceeded in 1941 to develop a combined magnetic-acoustic mine. Once more the Luftwaffe stultified the effect through premature laying.

By the end of the period the effectivness of the magnetic mine had seriously diminis-hed. The Germans began, as the basic for a policy of technical surprise, a systematic study of ships influence fields.

The second period, from the introduction of the magnetic-acoustic mine in the Sum-mer of 1941, to the end of 1943, was one of steady research but no essential novelties. In April 1942, the German Navy had approximately 50,000 mines of all types ready for operational use. Through 1942 the monthly demand for mines was extremely low and at a constant level. Subsequently, as Allied action became more aggressive, especially in the Mediterranean, the demand accelerated. Ironically, now that no new weapon were com-ing out and successful countermeasure for the old ones were in operation, the Luftwaffe took mining more seriously and put forward its biggest minelaying effort.

During the third period, from the beginning of 1944 to the end of the war, the desing work of the previous two and a half years bore fruit. The pressure, the low-frequency acoustic and variants of the audio frequency circuits came into service, and the Navy had under developemt a wide varity of other weapons. From 1940 on, the Allied had stu-died the technical problem involved in countering many of this weapons; but their use would, none the  less, have been very unwelcome.

The Germans had developed not only new types but also new techniques. Since no single mine is insurmountable, the weapon was the minefield, not the individual mine. Mine warfare operated on the principle of statistics. At the same time that German mines were becoming inereasingly complecated in firing principles, first the Luftwaffe and sub-sequently the Navy, late in the war, arrived at the general policy of laying mixed fields. These greatly increased the problem of sweeping.

The demand for mines reached its peak in the invasion year, 1944. By then the Naval High Command appreciated the value of mine warfare, but was forced to cut orders to conform with the maximum possible production. At the same time, the laying capacity of the Luftwaffe declined heavily as a result of the German reverses on all fronts. This took the sting out of the new armory of mines. E-boats, and other naval craft took over the mining offensive in the last stages of the war, but their scale of operations was necessa-rily small.

The Allied were fortunate that, very much at in the case of German submarines and torpedos, the bomber position was not in phase with the weapon position. If the Luft-waffe had negained its offensive power, the Allied mine defense would have deteriorated.

Figure 3 – Graph of Mine Laid.

Figure 4 – Mines Laid.

TOTAL NUMBER OF MINES LAID PRIOR TO OCTOBER, 1943

Year

Month

Total

Year

Month

Total

Year

Month

Total

3

9

3

4

10

4

5

11

5

6

12

6

7

1

7

8

2

8

9

5400