While the Union celebrated, the British were furious that their ship had been boarded and passengers removed. Their government protested this treatment and insisted that Mason and Slidell be freed. French leaders sided with England. While the incident was very popular in the North, President Lincoln and his advisers worried that it could lead to war in Europe. Therefore, by the end of December 1861, William Seward, Lincoln’s Secretary of State, admitted to the British that the incident should have gone through the courts. Following this, the . released the South's diplomats. In addition, the American government declared it was happy to see that England supported the idea of neutral seas. Disagreement over this had led to the War of 1812.
It is hoped, at all events, that this extremely disagreeable business will secure the end proposed by so much humiliation-namely, that we may be suffered to conclude the job of crushing out the rebellion without further foreign interference. At the present time a piratical steamer- the Nashville- belonging to the rebels, half filled with the plunder of the American ship Harvey Birch, which she burned within sight of the British coast, is refitting in the harbor of Southampton: the British steamer Gladiator, filled with arms and munitions for the rebels, is lying in the British port of Nassau, and has been supplied with coals to enable her to run into Savannah or some other rebel port, while the authorities of Nassau refuse coals to our gun-boat, the Flambeau, which is watching for her: other British steamers are notoriously fitting out in England with like cargoes for the rebels; and British officials all over, from the Governor of Canada to the Consul at Havana, give palpable evidence of their sympathy with the rebels. It is to be hoped that this measure of unfriendliness and injury may suffice. We do not trust that the British may be satisfied with equipping pirates to prey upon our commerce, and receiving them with their plunder; with converting British ports into harbors of safety for our enemy's ships, and refusing to sell coal to our vessels; with permitting their officials to receive with honor and respect the emissaries of the rebels, and to visit with their high displeasure any British subject who shows a friendly spirit toward this country. As we have treaties of alliance with England, and the members of the British Government are constantly assuring us of their high regard for us, perhaps these injuries may slake their dislike for the United States and for democracy. It is to be hoped, after the surrender of Mason and Slidell, that they will.