In late 1942, enemy activities in the Indian Ocean had virtually come to an end. The German raiders, once disrupting the shipping lanes in these waters had all (with the exception of a few) been destroyed by the Royal Navy or had begun the long way home to thehomeland in Europe. The Japanese were strategically not interested in sinking merchant ships, and had done little to sink them since their successful sortie to Ceylon in April 1942. But unknown to the allies, the Japanese Navy had decided to keep the pressure on the shipping lanes, mostly because of their ever growing importance in the war. Large and valuable tankers maintained a continuous stream of oil and other products from the Middle East to Australia and surrounding islands. The continuous pleas by the Germans will undoubtedly have had a large influence on this decision, as the Japanese were afraid the Germans would send more of their successful disguised raiders to the Indian Ocean, which the first considered "their backyard". The bond between the Japanese and Germans never grew as strong as the one between the Allied forces, and they distrusted each other from the very start of their alliance. To satisfy the Germans, the staff of the Imperial Japanese Navy decided to send their own raiders to these waters. Although raider warfare was not entirely strange to them, they could not build on the vast amount of experience as the Germans did, and as a result, their ships were far less effective.
In 1940, two passenger-cargo vessels of the Osaka Shipping Line were requisitioned for conversion to Armed Merchant Cruisers, in anticipation of the likely thrust southward by the Japanese. The Aikoku Maru and Hokoku Maru, under construction for the route between Japan and South America, started their rebuilds in 1941, and by the time they were commissioned, they were armed to the teeth. Their specifications were as listed below:
On November 11 at 11.45 in the morning, the naval authorities in Fremantle received a SOS-signal sent out by the Bengal, reporting that she and the Ondina were under attack by two enemy raiders, identified as being Japanese, in position 19.38 N - 93.5 E. The battle started when a lookout aboard Ondina sighted an unknown vessel at about 12000 metres away, bearing 270 degrees, followed by ship of similar size. As no allied ships were reported in the vicinity, they could only assume they were hostile and for some time these ships were even identified as Japanese carriers. On the Bengal, the lookouts saw the two AMCs a few minutes later. The ships both made a quick 90 degrees turn to starboard away from the enemy to a north-north-west direction. Bengal then turned and headed straight for the enemy, thus hoping to buy enough time for the Ondina to escape. She opened fire at 1200 hours from 3200 metres away, soon followed by the Ondina at 1205 8000 metres away. The sensible thing to do for the Ondina was to follow the order to escape, but the captain decided to stay, as his ship, armed with a 4-inch gun, was still the most powerful of the two. In addition, the Ondina could only do 12 knots versus 21 of the Japanese ships.
The Aikoku Maru (Captain Oishi Tamotsu) and Hokoku Maru (Captain Imazato Hiroshi) commenced firing at 1200 hours, and soon straddled the Ondina with their cruiser-armament. The first hit on Ondina ripped off a part of the main mast, leaving only a stump standing. The Ondina herself had her answer ready: the third shell fired was a hit in the superstructure of Hokoku Maru, but apparently did little to effect her speed or armament. Content with the hit, the gun captain then ordered the gunners to concentrate their fire on the stern. Only a few moments later, a lucky hit on the starboard torpedo mount turned the Hokoku Maru in a ball of red and yellow flames, and as the ship emerged from the smoke, she was listing heavily to starboard, and simultaneously started to settle by the stern. The explosion ripped off the stern and threw her two floatplanes overboard, while massive fires raged in the superstructure. Hokoku Maru was not built as a warship, and therefore didn't have a sufficient number of watertight bulkheads. Shells fell from their lockers as a result of the increasing list and threw sailors overboard. Men, covered with burns and blood tried to fight the flames. Reports came in indicating large fires in the engine room and the loss of all electricity. There was little hope of salvaging the Hokoku Maru, and Captain Imazato could do little else than to order "abandon ship". The Aikoku Maru soon avenged her sister ship, scoring several hits on Ondina. Fortunately, shells and torpedoes have little effect on empty tankers, as the large number of watertight tanks keeps them afloat under the most difficult circumstances. Aikoku Maru also fired at the Bengal, which had shortened the distance to about 2200 metres. One shell from the Japanese hit her in the forecastle, luckily doing little damage. Her gunners had been firing continuously at the Japanese, claiming several hits. Unfortunately, the ammo supply was soon depleted . At 1245, her last shell had been fired and her captain decided there was little he could do for the Ondina. He steamed away at full speed, chased by gun splashes. After laying a smokescreen, she took a hit in the stern which did little to hamper her escape. Last the men aboard Bengal saw was the Ondina trying to evade the shells, continuously straddled by the Aikoku Maru. A shell was seen hitting her abaft the bridge. Some time later, a second explosion was seen aboard Hokoku Maru, still burning and sinking. After leaving the scene, Bengal set course for Diego Garcia, where the captain reported the Ondina and one enemy AMC sunk.
Bengal's captain was right about one thing, the Hokoku Maru had indeed sunk, but after Bengal had disappeared behind the horizon, Ondina was still steaming around at full speed. Not built as a warship, she had only a small ammo supply. Aikoku Maru closed the range to 3500 metres, and placed several hits in the following minutes, one of which was observed by the Bengal. Ondina herself had only 12 shells left, four of which she fired at the Hokoku Maru, the rest at Aikoku Maru, apparently without placing a hit. A last attempt to escape by dumping smoke buoys overboard was unsuccessful, and the captain ordered the crew to abandon ship to avoid further bloodshed. The engines were stopped, the lifeboats lowered and a white flag was hoisted, all under continuous fire from the Aikoku Maru. A few moments later, Captain Horsman was killed by a piece of shrapnel from a shell hitting the bridge. Two lifeboats and two rafts were lowered into the water and later, another lifeboat was in the water with the remainder of the crew. Most of the crew (with the exception of officers and gun crew) consisted of Chinese, and they had been troublesome during the whole action, refusing any assistance that might help save the ship. Aikoku Maru approached Ondina to about 400 metres, and fired two torpedoes to finish the ship off. Both slammed big holes in the starboard side, but did little to sink the ship itself. These tanks had been empty and the ship remained afloat on the other, undamaged fuel tanks, despite the 30 or 35 degrees list. Then Aikoku Maru changed course and the Japanese gunners opened fire on the drifting lifeboats . One sailor was killed, with three others heavily wounded. One of them was a young British sailor named Henry, originally assigned to the Bengal. Satisfied with the results, Aikoku Maru then steamed away to pick up survivors from Hokoku Maru . Later, the Aikoku Maru came back one more time, firing a torpedo which missed the tanker. She paid little attention to the survivors and steamed further, convinced the Ondina was doomed . Meanwhile, the men in the lifeboats had given the deceased a seaman's burial, and then exchanged thoughts about what to do next. The first officer Rehwinkel wanted to return to the tanker, but only one man of the gun crew was willing to go with him. Most of the others were convinced the Ondina was about to go down. Not without trouble, Rehwinkel managed to assemble a small number of men and returned to the ship, where counter flooding reduced the list. Inspection revealed that her engines were also still intact. The small fires were extinguished and the last crewmembers in the lifeboats were taken aboard, after the latter were convinced there was no danger of sinking. Now the long leg back to Fremantle began. The lifeboats were patched up as good as possible, in case the Aikoku Maru came back. The British sailor Henry was in very bad shape. He had a crushed leg and after two days the first officer was forced to send out an uncoded signal for help. Uncoded, because the codebooks had all been thrown overboard when "abandon ship" was ordered. This unexpected signal caused a shock in Colombo, as the Ondina was reported sunk and logically, the British thought the Japanese were playing a trick on them. A signal went out from Fremantle to report her position. Expecting a trap by the Japanese, the Ondina didn't reply. Without medical attention the Ondina steamed towards Fremantle. Fortunately, on the 17th an Australian Catalina flying boat was sighted, about 200 miles northwest of Fremantle. The lookouts had reported a ship some time earlier, and the Catalina was asked if that ship could provide the much needed help. The unknown ship proved to be a hospital ship , where doctors immediately began a series of blood transfusions to save Henry's life, and with success. On 18 November, the Ondina entered Fremantle after a journey only a few ships had experienced, let alone lived to tell about it. The corvette Bengal had entered Diego Garcia the day before. Ondina remained in Australia as depot ship until 1943, when she was finally repaired. Both Bengal and Ondina survived the war.
Very few questions remain concerning this clash, but the most important is who fired the fatal shot? Answering this question is difficult, as both the Ondina and Bengal claimed to have scored the fatal hit and this mystery may never be solved. The Japanese themselves thought it was the Ondina. According to them, her shell hit the starboard torpedo launcher, causing the torpedo to explode. At the time, the Bengal was given the benefit of the doubt, according to the author of my main source as an attempt to use this battle for propaganda in India, where the British had a lot of trouble keeping the people under control. In retrospect, this battle not only was a tactical success for the Allies, but also it also had strategical implications. The loss of the Hokoku Maru led to the abandoning of raider warfare by the IJN, and never (with one exception) tried to break the lifeline again. Ondina was given a rare Dutch distinction, the Koninklijke Vermelding by Dagorder, issued on July 9, 1948. Captain W. Horsman became Ridder in de Militaire Willemsorde der 4de Klasse posthumously and was Mentioned in Dispatches, while gunner Hammond received the Distinguished Service Medal and the Bronzen Kruis. The captain of the Bengal, Lieutenant-Commander Wilson, received the Distinguished Service Order, while others of his crew were also awarded.
 Eiichi Nakajima: "Hokoku Maru - the unknown Q-ship"
lists the number of victims as 8. I have been unable to identify the
other three, if there were any more. Their results were as follows:
 Captain Imazato Hiroshi was born in Nagasaki on September 24, 1896. He graduated from the Etajima Naval College in November 1917, and then took went to the Torpedo School in Yokosuka, and later specialized in submarines, becoming commander of the 20th Submarine Division in November 1939. On August 11, 1941, he became commander of the 1st Submarine Division and switched to the 2nd Division in February 1942. He eventually became commander of Hokoku Maru on August 25, 1942. He was promoted to Rear-Admiral posthumously.
 According to Warship International, she had an ammunition supply of only 40 shells
 Captain Oishi Tamotsu of the Aikoku Maru was born in Kochi in 1900, and graduated from the Japanese Naval College in 1920. He then specialized in navigation, and had some ship assignments until his graduation from the advanced course of the Navigation Naval School in 1926. He received his first command in 1938 (gunboat Saga). In October 1940, he was appointed senior staff officer of the 1st Carrier Division. From following April, he had the same function with the 1st Air Fleet. As staff officer, he participated in all major carrier operations from Pearl Harbor to Midway, and then took command of the Aikoku Maru in August 1942. On April 3, 1943, he was relieved from his command and held several positions until the end of the war. He died on February 13, 1946 and was promoted to Rear-Admiral posthumously. Apparently, he was never tried for machine-gunning the survivors of Ondina.
 The Aikoku Maru picked up a total of 278 survivors of a crew of 354. Captain Imazato was one of the 76 killed during the action. I haven't found any mention of damage or casualties aboard the Aikoku Maru.
 Aikoku Maru became a high-speed transport and was sunk in February 1944 during the Operation Hailstone, the bombardment by American aircraft of the Japanese base at Truk. The wreck is still very popular by divers.
 I have been unable to identify this ship. More info is appreciated.
K.W.L. Bezemer: "Verdreven doch niet verslagen"
Eiichi Nakajima: "Hokoku Maru" - the unknown Q-ship (an extract was kindly provided by Sander Kingsepp)
Thanks to Roel Zwama, Anne Niemantsverdriet, Bert Kossen, Jean-François Masson and Dan Muir for providing additional details.