Complex sentence: There are a number of contributing factors to this situation, large amounts of documentation were lost in the burning of municipal buildings in Brussels in 1695 while a great many archives were destroyed in bombing campains in the two world wars.
Split into simpler sentences: There are a number of contributing factors to this situation. Large amounts of documentation were lost in the burning of municipal buildings, for example in Brussels in 1695, while a great many archives were destroyed in bombing campains in the two world wars.