I think this song is talking about the Battle of Hong Kong in 1941. The Battle took place from December 8, 1941 and went until Christmas Day, 1941. Violet Hill, a location in Hong Kong, was used by the Japanese to bomb Aberdeen during this battle.
At the end of the song, when he talks about taking his love to Violet Hill, it fits, because Violet Hill would be a good place to view where the battle took place. The battle was fought in urban areas as well, so the "rooftops" line fit.
British, Canadian, and Indian soldiers all fought against the Japanese. The Japanese won the battle.
Chris is British, so it could be describing the story of one of his relatives? I am not sure, but this song seems to fit the battle.
http://en.wikipedia.org/wiki/Violet_Hill
http://en.wikipedia.org/wiki/Battle_of_Hong_Kong