Neutral shipping in the Spanish Civil War

Spain depended heavily on maritime imports, so Republican and Nationalist forces both sought to interrupt supplies reaching enemy ports. Michael Alpert's account distinguishes a warning that ships entered a war zone at their own risk from a formal declaration of blockade. The quoted Admiralty instructions allowed British warships to resist definite aircraft attacks outside Spanish territorial waters immediately, without warning. Attacks by warships were to be resisted if they continued after remonstrance. The instructions used a three-mile territorial limit, warned British merchant vessels to remain outside it, and advised British warships to avoid berthing near Spanish warships. These distinctions governed how neutrality could be defended without treating every encounter in the same way.