Complex sentence: The building was only to be used for six months by the public at which point it was to be dismantled, however World War Two meant that the site and some buildings were used by the New Zealand Airforce until the end of the war.
Split into simpler sentences: The building was only to be used for six months by the public at which point it was to be dismantled. However, during World War II, the site and some buildings were used by the New Zealand Air Force until the end of the war.