Complex sentence: During 1664, tensions between Britain and the Netherlands rose with rumours of war being imminent--that same year, Commander Zacharias Wagenaer, successor to Jan van Riebeeck, was instructed by Commissioner Isbrand Goske to build a pentagonal fortress out of stone.
Split into simpler sentences: During 1664, tensions between Britain and the Netherlands rose with rumours that war was imminent. That same year, Commander Zacharias Wagenaer, successor to Jan van Riebeeck, was instructed by Commissioner Isbrand Goske to build a pentagonal fortress out of stone.