Complex sentence: After Russia leased Port Arthur (130 kilometres across the sea in Manchuria) from China for 25 years in March 1898, the United Kingdom obtained a lease for Weihaiwei which was to be in force as long as the Russians occupied Port Arthur.
Split into simpler sentences: After Russia leased Port Arthur (130 kilometres across the sea in Manchuria) from China for 25 years in March 1898, the United Kingdom obtained a lease for Weihaiwei. This lease was to be in force as long as the Russians occupied Port Arthur.