What were the naval doctrines of the main naval powers in the 30's (prior to the outbreak of WWII) and how they influenced actual ship designs and operations? I will try to outline some, will appreciate your additional info and corrections. USA Focus on Pacific, but Atlantic also an issue long distances --> large submarines, long range ships in general limit to ship size due to Panama canal (was this an issue already prior to the war?) to be 50% larger than the main opponent, that is Japan (as a naval policy) ? Fleet operations BB heavy, CVs as support ? GB Focus on opened sea lanes + empire protection lot of ships required --> smaller designs? (e.g. DDs) need for long range and good seaworthiness --> lighter armament in comparison ? Fleet operations BB heavy doctrine Role for CVs? ?? Japan Competition with super powers in the pacific not able to field as many ships as competitors (US, GB) --> requirement for very heavy armament to compensate long distances --> large SSs, longe range in general ? Fleet operations decisive battle approach most advanced CVs doctrine focus on night ops ? France I do not know Italy Focused on the Med: short distances --> lower fuel capacity calmer sea compared to e.g. Atlantic --> lower sea keeping qualities required Fleet operations: ships do not fight at night what was the focus? Decisive battle / defence / interdiction? Germany Countering England, France Commerce interdiction, but surprisingly little focus on submarines Need to win over RN --> plan Z ? Fleet operations BB heavy very little consideration given to CVs (plus fat Hermann interfered) ?