Tuesday, 2 March 2021

The Asama Maru Incident: Implications for today

On the 6th January 1940, the still relatively new Asama Maru, a medium-size Japanese ocean liner, left San Francisco on the homeward trip of Nippon Yusen trans-Pacific Orient-California fortnightly service. Amongst the approximately 800 passengers, were 50 German merchant seamen – from various vessels, but all carrying the same aim – travelling home to Germany. A task which the British blockade had made all but impossible for warships of the Kreigsmarine, let alone slow merchant vessels. Their plan therefore was to get across the Pacific, across Russia via the trans-Siberian railway, to the other side of the world – Germany. It sounded like a good plan, on paper it might have even read as one; however, those who put it together forgot the underlying nature of British power.

This is not saying that those organising this project had not considered the fact that the Royal Navy had forces in the Western Pacific (although they probably presumed the British would not be so brazen, so confrontational, as to stop/board a Japanese ship). They had. What they had not considered was the informal power and presence that decades, even centuries, of British commitment and interaction had built up within the Pacific space, something which was further enhanced by the experience and knowledge the Royal Navy’s officers had accrued serving in the region, especially those that had been deployed time and time again throughout their careers. It was these factors that would enable the British course of action.

HMS Liverpool, a Town class light cruiser, had already been on patrol when Asama Maru left port. In fact, it was on the 16th January that HMS Liverpool had started out from Hong Kong to begin its second patrol; during its previous patrol (that had started on the 23rd December) it had stopped three ships and boarded them – just on the possibility they might be carrying Germans. All in contrast to the assumptions the German plan had been predicated upon; but their issues would not end there.

On the 20th January, 14 days after Asama Maru had put to sea, HMS Liverpool received notices that the ocean liner was carrying German sailors. Some were believed to have come from the Norddeutscher Lloyd passenger ship Columbus, which had been scuttled by its crew when they feared capture by the destroyer HMS Hyperion, with the crew having been picked up by the cruiser USS Tuscaloosa. The day after receiving the update, HMS Liverpool, taking full advantage of her officers’ prior knowledge of the sea lanes, intercepted the Asama Maru 35 miles off the Nojima Promontory (Chiba Prefecture, practically next to Tokyo) at 12:55 (local time) – in international waters and just out of sight of land.

The actual stopping and boarding was fairly straight forward, involving only the use of a three pounder signal gun. The use of this little gun would within 24 hours reverberate around the world. The captain of Asama Maru protested, naturally, but faced with twelve six inch guns distributed evenly across four turrets supporting an armed, but firmly polite, boarding party quickly placed aboard his ship, he had to concede. All 50 Germans were discovered, but upon reading their papers only 21 were removed from the ocean liner to be taken back to Hong Kong. The Asama Maru proceeded to Yokohama at best speed.

Was it legal?

Within 20 minutes of being stopped, HMS Liverpool’s boarding party, under the command of Lt Cdr G H Greenway, Lt C D Madden and Lt (E) M E P Studdert was aboard; the fact it had three officers stresses the size of the boarding party, as well as the delicate nature of what it was about to do. Whilst Greenway and Studdert went to the bridge of the Asama Maru, Madden took over the First Class Lounge as a place to secure the German passengers when they were found. The debate as to the legality of the action started immediately. The Asama Maru’s captain refused to admit any right to remove German passengers from his ship:

…stating that by international law, it was only contraband cargo that belligerents were entitled to remove from neutral ships on the high seas. He also stated that he had made a voyaged from London to Kobe, commencing about 21st August 1939 with German Passengers aboard…no attempt had been made by British authorities to remove any Germans…

To which the response from Greenway was:

…by international law I was fully entitled to remove from his ship as prisoners of war German subjects who were returning to their country to assist in the war effort. With regard to his voyage from London to Kobe I told him that the reason why no action was taken was probably because his voyage started before war had been declared…

It was all concluded aboard the Asama Maru within an hour and twenty minutes, with the last Royal Navy personnel leaving the vessel at 14:35 – in total it had been delayed an hour and forty minutes – a long time in the life of an ocean liner, but it would have been a lot longer if her crew had not proved so helpful to the Royal Navy’s boarding party. The initial interrogations conducted by Studdert actually showed that not all British information had been reliable, rather than mostly coming from the Columbus, most of the merchant seamen came from the by then Panama Transport Company, formerly Baltic American Petroleum Company – both of which were subsidiaries of Standard Oil Company. It was also found that as a far as they knew it was their employers, who did not want to keep paying them if they could not use them, that had arranged their journey home.

The Japanese based their opposition to the action on Article 47 of the Declaration of London, a treaty that had never been ratified by any state, so had never come into force. However, if this problem is overlooked, the in fact the problem comes from the wording of Article 47 itself:

Any individual embodied in the armed forces of the enemy who is found on board a neutral merchant vessel, may be made a prisoner of war, even though there be no ground for the capture of the vessel.

The problem is the ‘Any individual embodied in the armed forces’, now on the surface it sounds straight forward it must surely mean just those serving; the trouble is that every state had their own definition of what this meant. After all, what about reservists or those with skills which rapidly translate to military needs, making them de facto reserves? Most countries agreed they were military people; Germany, whose definition from its 1939 Prize Ordinance is below, certainly did:

(1) The passengers in captured vessels must be released.

(2) The following are excepted: –

(i) Members of the enemy armed forces.

(ii) Persons who are making the voyage in order to put themselves in the service of the enemy armed forces.

(iii) Agents of the enemy.

As such, the Japanese, by claiming the British were acting illegally, were actually making a claim the Germans neither could nor would have made themselves. They knew this, so why do it? Simply put, geography. It had happened so close to Japan, any closer and HMS Liverpool would have been plucking them off the Asama Maru in Japanese waters. The interesting scenario under those circumstances is whether the Royal Navy would have gone full ‘Altmark Incident’ – i.e., when it followed the Kriegsmarine tanker Altmark into a Norwegian Fjord or whether it would have backed down.

As it was, it was a humiliation for the Imperial Japanese Navy, especially when it was found out by the press that HMS Liverpool and other cruisers, had been stopping and searching many ships – often with less dramatic results, but with definite regularity. For the Japanese High Command, it was a dramatic illustration of difficulties of protecting trade, even if few lessons were learnt from it.

After the initial flurries of outrage, serious negotiations took place and whilst the British ended up deciding to return nine of the captured sailors, the incident ended with an agreement by the Japanese not carry any more Germans. This effectively shut off this route home for the Germans, before the invasion of the Soviet Union would have.


For the Royal Navy the Asama Maru Incident was a double-edged sword. Although the incident revealed to the Japanese the capacity of British cruisers, maximising their deterrent value, it also made their numerical reduction, as a result of Italy’s entry into the Second World War, all the more telling. The big plus though was undoubtedly the 1,000 or more German merchant seamen in the Pacific who never tried to make it home. They realised that whatever they did, a British cruiser would be waiting for them, even if Germany’s invasion of the Soviet Union and declaration of war against the United States (US) were major factors in compounding their realisation.

In 1940 there was quite a comparatively narrow definition of who might be considered viable military personnel; modern warfare, having expanded to include cyber warfare, information warfare, as well as others alongside the more traditional forms, has served to multiply the numbers of potential service personnel. What is more the options for redress, for appeal, are limited and pragmatically toothless.

In such circumstances, therefore, while every country might like to have the global reach Britain did in 1940, very few nations today enjoy the advantages of a globally deployable naval fleet – with the infrastructure and connections to support it. Even those nations that retain such an advantage will still need to think about how they go about extracting those persons who might be useful to their war effort or whose loss might adversely affect it; after all, a popular social media influencer spouting enemy propaganda from a controlled environment could prove very complicated; it may even force governments into actions they would never have previously considered. More traditionally though the loss of engineers and scientists – the fuel of the intellectual struggle which has typified great power contests since the nineteenth century – could prove a major issue, especially for those nations who rely upon their technological edge to compensate for mass limitations.

This article was made possible due to the kind support of the Engelsberg Programme for Applied History, Grand Strategy and Geopolitics at the Centre for Geopolitics, supported by the Axel and Margaret Ax:son Johnson Foundation for Public Benefit.

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