Here are a dozen enemy ships from 1942 and a number of look alikes. If you spotted these ships at sea from an aircraft and without a manual or chart in hand, do they appear easy or difficult to identify?

According to the Office of Naval Intelligence (ONI) mistaken identity was a problem for those who had to contend with the Japanese and German navies. ONI published identification manuals to assist in determining if a vessel was friend of foe.

ONI 204, published by the Division of Naval Intelligence in October 1942, contained a "one stacker chart" which stated:

"Timely identification in wartime may often mean the success or failure of an operation. Design similarities present a peculiar problem. This is strikingly illustrated in the case of the German navy, which insofar as its major units are concerned, may be termed a one-stacker navy. Attention is invited to the ONE STACKER CHART. This page further develops cases of easily mistaken identity by illustrations of types which might easily be confused with the main German naval units by the untrained observer."

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