In 1908 the Commonwealth had been divided into several independent states under democratic Allied-sponsored governments. As these governments appeared to be favouring the cause of the West rather than that of their own countries, a large proportion of the people soon became disillusioned and became nostalgic for the old days. The democratic cause was not helped by the prior involvement of a number of its leaders in negotiating the humiliating terms of the Treaty of Prague, leading to accusations of national betrayal and a search for a scapegoat.
Between 1916 and 1925 several former Commonwealth countries saw the establishment of National Socialist movements, which emphasised the superiority of Commonwealth culture and called for the Treaty of Prague to be overturned. This message resounded with many, leading to National Socialists coming into power in some areas, whether by election or revolution. In either case, they soon started to silence their political opponents.
A series of brutal civil wars broke out between supporters of the democratic and nationalist movements. Although the former Allies supported the democrats diplomatically, they were too complacent to get directly involved in the war. By 1928 the nationalists had emerged victorious throughout most of the former Commonwealth, and in December of that year the leaders of Lithuania, Poland, Ruthenia and Russland gathered in Vilnius to sign the Treaty of National Union .
The new UNSR expanded aggressively, forcibly incorporating several other republics who had refused to sign the treaty. For most of this period the Allies pursued a policy of appeasement, not wishing to get involved in another war. However, the final straw came in 1939 when the UNSR invaded Finland. Albion and Saxony declared war three days later, and the Third World War had begin.
Working with similarly minded parties in other European states, the UNSR saw remarkable success early on, overrunning most of continental Europe by 1941. However, its remaining enemies unexpectedly refused to seek peace terms and started to fight back, forcing a stalemate and the establishment of a ceasefire by 1948. Per the terms of the ceasefire, the UNSR agreed to evacuate some of the territories it occupied, though not before establishing friendly governments in them.
The ceasefire broke down in 1961. This time, however, the UNSR was not prepared for war, having spent the time trying to keep its conquests subdued rather than developing its military technology, and it soon found itself on the defensive. By 1964 the UNSR's armies were being pursued back into their own country, before being trapped and annihilated by the late and unanticipated intervention of Altai. The union surrendered unconditionally in September of 1965, and was dismantled by the victorious Allies.