Mirabile Illud is an encyclical of Pope Pius XII on the crusade of prayer for peace, given at Rome from St. Peter's on the sixth day of December, the year 1950, the twelfth of his Pontificate. The Pope is concerned about imminent war spreading from the Korea to the world. Bloody conflicts bring in their wake untold ruins, slaughter and misery of every kind. He exhorts all to put aside animosities and differences and introduce that true peace. But, because human efforts are incapable of achieving such results, he institutes a prayer crusade for the whole Church.