Decenium Dum Expletur (September 1, 1949) is an Apostolic Letter of Pope Pius XII to the bishops of Poland about the suffering of the Polish People. The Pontiff describes his peace policies before World War Two, aimed at avoidance of the war. “Nothing is lost with peace, everything may be lost with war”. We tried everything with all means at our disposal to prevent the taking up of arms and to seek an honourable solution for all sides.