By May 1945, the German Navy and the Luftwaffe had either laid or undertaken the development of an imposing array of 96 different types of naval cases. This total does not take into consideration captured foreign mines which the Germans used. The mines fall into two separate groups – contact and influence.

Contact Mines. The Germans started World War II with seven different types of moo-red contact mines: the EMA, EMB, EMC, EMD, FMB, FMC, and UMA. The EMA and EMB, identical except for the weight of charge, were World War I mines designed for laying by submarines. A limited quantity were laid during World War II out of stocks remaining on hand. The Japanese JA mine, used operationally in the Pacific after 1941, was a copy of the EMA.

The German Navy developed the remaining five types between 1923 and 1939. It pla-ced especial emphasis upon the EMC, which was the most widely used and the most adaptable. During the course of the war, the Navy made major changes in chain mooring; added cork-floated snag lines, mounted antenna and mechanical cutters on the mooring cable; and in other ways improved these types to remedy defects or conform with changing military requirements.

In addition, a number of new contact mines were developed. The UMB, a larger UMA, was designed; an aircraft-laid, moored, contact mine, the BMC, was introduced; the EMS series of drifting, decoy, contact mines were readied for operational use; the OMA series of moored, surface-contact mines and the EMG shallow-water, contact-depth assembly appeared. This group of moored contact mines was fortified by the development of a ground contact mine made of concrete and known as KMA. With this mine arsenal, the Germans had a series of diversified Naval mines adequate for composing a contact mine-field that would meet the requirements of any given tactical need.

Contact-Influence Mines. Two interesting contact-mine developments were under-taken during the war. The first of these was the design of two combination contact-in-fluence mine cases, the EMK and EMU. These mines were intended to overcomes the fol-lowing shortcomings found in previous German moored mines:

1. In deep water, hydrostatic pressure sometimes prevented arming by counterbal-ancing the pull of the mooring cable.

2. In shallow water, rough seas caused excessive arming and disarming.

3. The use of explosive containers within the mine reduced the damage radius and served to render proper mine orientation more difficult.

4. The plummet-type standard surface anchor was not suitable for delayed-rising mines.

Since this development was assigned a low priority it proceeded at a slow pace and was never completed.