 The bloody standoff at Antietam in September 1862 , that ended Lee 's first major incursion into the North , gave Lincoln the confidence in Union arms he needed to announce the Emancipation Proclamation . British newspapers mocked Lincoln for hypocrisy in freeing slaves only in Confederate @-@ held areas , where he could exercise no authority . British officials had been shocked by the outcome of Antietam — they had expected Lee to deliver another brilliant victory — and now considered an additional reason for intervening in the conflict . Antietam , the bloodiest day of the war , had been a stalemate ; they read this as presaging an overall deadlock in the war , with North and South at each other 's throats for years as Britain 's mills sat empty and its people starved . France agreed with this assessment . 
