Belgian Congo. The line reached the Congo border in 1928. In 1914, both Angola and Mozambique had Portuguese army garrisons of around 2,000 men, African troops led by European officers. With the outbreak of World War I in 1914, Portugal sent reinforcements to both colonies, because the fighting in the neighboring German African colonies was expected to spill over the borders into its territories. After Germany declared war on Portugal in March 1916, the Portuguese government sent more reinforcements to Mozambique (the South Africans had captured German South West Africa in 1915). These troops supported British, South African and Belgian military operations against German colonial forces in German East Africa. In December 1917, German colonial forces led by Colonel Paul von Lettow-Vorbeck invaded Mozambique from German East Africa. Portuguese, British and Belgian forces spent all of 1918 chasing Lettow-Vorbeck and his men across Mozambique, German East Africa and Northern Rhodesia. Portugal sent a total of 40,000 reinforcements to Angola and Mozambique during World War I. By this time, the regime in Portugal had been through two major political upheavals—from monarchy to republic in 1910 and then to a military dictatorship after a coup in 1926. These changes resulted in a tightening of Portuguese control in Angola. In the early years of the expanded colony, near-constant warfare was occurring between the Portuguese and the various African rulers of the region. A systematic campaign of conquest and pacification was undertaken by the Portuguese. One by one, the local kingdoms were overwhelmed and abolished. By the middle of the 1920s, the whole of Angola was under control. Slavery had officially ended in Portuguese Africa, but the plantations were worked on a system of paid serfdom by African labour composed of the large majority of ethnic Africans who did not have resources to pay Portuguese taxes and were considered unemployed by the authorities. After World War II and the first decolonization events, this system gradually declined, but paid forced labor, including labor contracts with forced relocation of people, continued in many regions of Portuguese Africa until it was finally abolished in 1961. Post-World War II In the late 1950s, the Portuguese Armed Forces saw themselves confronted with the paradox generated by the dictatorial regime of the Estado Novo that had been in power since 1933; on one hand, the policy of Portuguese neutrality in World War II placed the Portuguese Armed Forces out of