In Biggles in Borneo, General Yashnowada was a Japanese Army officer and held a position akin to that of a military governor of occupied territories which included parts of Mindanao and Borneo. Yashnowada kept his headquarters in Cotabato on the Filipino island of Mindanao where there was also a prison camp in which the Japanese had concentrated some Allied prisoners of war as well as civilian internees.
According to escaped prisoners Jackson, Bill Gray and Pat Flannagan, conditions at the Cotabato prison camp had been tolerable until the arrival of Yashnowada. Yashnowada had instituted a regime of terror--flogging prisoners for various offences. Bill Gray himself had been flogged after a failed attempt to escape. Yashnowada had also beaten the American General Barton in order to force him to reveal military secrets.
After Algy and Ginger had bailed out of their Beaufighter and had been captured by Japanese soldiers, they were taken by a submarine to Cotabato where they came face to face with Yashnowada. Yashnowada was described as short, icnlined to stoutness, with a broad face in which the cheekbones were conspicuous. He wore horn-rimmed spectacles and had a small black moustache, drooped round the corners of a thin-lipped mouth. Yashnowada question Algy and Ginger in English. Yashnowada had heard about the existence of Biggles' secret squadron and had scouts out everywhere looking for it. He therefore demanded to know if Algy and Ginger belonged to the squadron. Algy refused to say more than was required by the rules of war even though Yashnowada threatened that every member of the squadron he captured would take 24 hours to die. Not having any success, Yashnowada dismissed Algy and Ginger, promising that he had ways to make "the very dumb speak".
Fortunately for Algy and Ginger, the rest of their squadron soon attacked Cotabato and freed all the prisoners. This, however, was accompanied by much bad luck later when a Japanese marine aircraft spotted Lucky Strike, leading to a series of air raids which effectively destroyed the squadron's aircraft. Meanwhile, Yashnowada landed at Brunei with a strong force of troops intending to make his way to Lucky Strike and wipe it out. He plans were foiled when Allied Headquarters decided to reinforce Lucky Strike, sending, in the first instance, six Beaufighters which Biggles used to attack the advancing Japanese troops who had concentrated in a valley about 30 miles away. This air attack was then followed by a ground attack mounted by Suba and over two hundred of his Penan warriors. The Japanese force was wiped out and Yashnowada's death was confirmed when Ginger spotted his head impaled on a spear, being used as a trophy by Suba, Kalut and the rest of the Penan warriors.