Beginning in 1814, drought and blight caused the Oceanykan food market to collapse, bringing a famine of unheard of proportions. For more than 20 years, mounted raiding parties had infiltrated on each other's agricultural heartlands through the Outback in daring chevauchée attacks, better known as scorched earth tactics. Also, much of the population had been conscripted and perished in the battlefield, leaving an ever smaller workforce to tend the fields. With lower nutritional intake came a weakened immune system, allowing disease to ravage both armies and the civilian population. About thirty million people perished in these four years from a diverse number of causes, including increasing banditry and the outbreak of civil wars.
The British Empire's participation in the Great Collapse cannot be denied, and it remains a subject of international disagreements with said nation. In 1815 the Napoleonic Wars ended following Bonaparte's defeat at the Battle of Waterloo, signalling the beginning of Britain's golden age. King George III's first objective as newfound hegemon was to secure the two most economically promising and yet vulnerable regions in the world; Oceanyka and India. The former's territory was de facto already under significant control by Britain, as facing societal collapse, about a third of all city-states and groups had pledged vassalage to the British crown. Over these four years of collapse, Britain invaded or bought out whichever states hadn't yielded yet. The British embargoed the entire island save for their own subjects, making food imports impossible. Land whose owners had perished was seized by the crown, and then handed over to British settlers.
No truce or armistice was ever declared or agreed on by the Third Empire and its enemies. On November 4th, 1818, the British parliament declared sovereignty over Australia, thus beginning the Early Colonial Age. Remnants of the former national project were mercilessly hunted down by redcoats.