Tapioli, an Arowe man from Ainbul village in West New Britain, was working for the Department of Agriculture in Rabaul when New Britain was invaded by Japanese forces in 1942. He, along with many others, was taken into forced labour by the occupiers and transported to the mainland. Escaping at the first opportunity, he joined the Allied troops and enlisted with the Papuan Infantry Battalion (PIB). Tapioli later recalled that there were few formalities in the enlistment process. If you could walk and you could talk then you were considered fit for duty.

Tapioli served with the PIB for two years. He served at Nassau Bay, Tambu Bay and Salamaua in Morobe Province and led numerous patrols. He was later transferred to the 2 New Guinea Infantry Battalion. On 6 Feb 1945 he led a protest over uniforms among the NGIB troops that exposed tensions over race and equality within the unit. Soldiers of the NGIB were told to wear their stripes on their laplap rather than their shirt sleeves like the Australian soldiers. Tapioli stated that he would rather wear no stripes than wear them on his laplap, which he saw as the insignia of domestic duties and inferior to real soldiers such as those who had come from the PIB. Tensions boiled over into a brawl between the New Guinean and Australian troops. At the subsequent inquiry, Tapioli testified that he had spoken to Australian and African American soldiers who told PIB members about their higher wages and conditions of service.

Following the war Tapioli joined the Royal Papua New Guinea Constabulary, giving eight years of service to the police force and reaching the rank of sergeant.