Portugal established its monarchy in 1128. In the 19th century there was a dramatic growth in republicanism as a result of royal extravagance, a reactionary Church and large-scale poverty. In February, 1908, Carlos I and his brother were assassinated. After a insurrection in October 1910, Manuel II fled to England. Manoel de Arriaga became Portugal's new leader.

In 1914 the Portuguese Army began skirmishing with German troops on the frontier between Portuguese East Africa (Mozambique) and German East Africa. German agents also attempted to incite a tribal uprising in Angola. However, the Portuguese Army contained only 33,000 men and was not in a good position to declare war on Germany.