Why cut the military budget?

whilst i agree with many of David Cameron's measures i would ask him to look at the history books and remind himself of how unprepared the UK was at the outbreak of WW2, the scrapping of the Harrier Jet is a massive mistake, and such a versatile attack/defence weapon should not be lost to our arsenal, please re think your military / defence strategy again, and do not leave us unprotected as we were in 1939