Complex sentence: This coincided with a series of renewed military expeditions on the hinterland, and by the mid-nineteenth century Portugal had established its dominion as far east as the Congo River and as far south as Mossâmedes.
Split into simpler sentences: This coincided with a series of renewed military expeditions into the hinterland. By the mid-nineteenth century Portugal had established its dominion as far east as the Congo River and as far south as Mossâmedes.