preinvasion
adjective
pre·in·va·sion ˌprē-in-ˈvā-zhən 
variants or pre-invasion
: taking place in the period immediately preceding a military invasion
preinvasion bombardment
London in that preinvasion spring seemed full of color and gaiety. Uniforms of different nations abounded, and the air was charged with excitement and a tense anticipation.
Louis Auchincloss
Louis Auchincloss
Word History
First Known Use
1926, in the meaning defined above