What happens to interned military personnel if war is declared post-internment?

Question

Here is a real-world example during World War I. The German ship SMS Geier sails to neutral port in Hawaii in 1914, territory of the United States. Since the USA and Germany are not at war, the ship is interned. Presumably the crew are interned as well. Then, three years later in 1917, the United States declares war on Germany. What is the legal status of those original sailors?

Do they automatically become prisoners-of-war? Is there another legal mechanism in-place for this?

Assume that both warring parties are signatories to the Geneva Conventions, and follow them; as well as any other major international treaties and agreements that relate to diplomacy and war.

Answer 1

The SMS Geier was interned in November 1914 under Article 24 of the Convention Concerning the Rights and Duties of Neutral Powers in Naval War, which formed part of the Hague Convention of 1907. The crew were detained under the terms of the same Article, and for the duration of hostilities.

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When the United States entered the war on 6 April 1917, the crew of the SMS Geier became enemy combatants, and as such their status would have automatically changed to Prisoners of War (POWs).

The First Geneva Convention, adopted in 1849, and revised in 1906, only covered the treatment of sick and wounded enemy combatants. If any of the crew of SMS Geier were sick at the point that the US entered the war, their treatment would have been covered by that treaty.

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Interestingly, there were no internationally agreed rules governing the protection and treatment of POWs until the Third Geneva Convention was ratified in 1929.