Meanwhile the work of transferring Butler's forces by sea to Ship Island had been going on with vigor. He had raised thirteen regiments of infantry, ten batteries of light artillery, and three troops of cavalry, numbering in all about 13,600 men. To these were now added from the garrison of Baltimore three regiments, the 21st Indiana, 4th Wisconsin, and 6th Michigan, and the 2d Massachusetts battery, thus increasing his force to 14,400 infantry, 275 cavalry, and 580 artillerists; in all, 15,255 officers and men. On the 23d of February, 1862, Butler received his final orders: "The object of your expedition," said McClellan, "is one of vital importance--the capture of New Orleans. The route selected is up the Mississippi River, and the first obstacle to be encountered (perhaps the only one) is in the resistance offered by Forts St. Philip and Jackson. It is expected that the navy can reduce these works. Should the navy fail to reduce the works, you will land your forces and siege-train, and endeavor to breach the works, silence their guns, and carry them by assault. "The next resistance will be near the English bend, where there are some earthen batteries. Here it may be necessary for you to land your troops to co-operate with the naval attack, although it is more than probable that the navy, unassisted, can accomplish the result. If these works are taken, the city of New Orleans necessarily falls." After obtaining possession of New Orleans, the instructions went on to say, Butler was to reduce all the works guarding the approaches, to join with the navy in occupying Baton Rouge, and then to endeavor to open communication with the northern column by the Mississippi, always bearing in mind the necessity of occupying Jackson, as soon as this could safely be done. Mobile was to follow, then Pensacola and Galveston. By the time New Orleans should have fallen the government would probably reinforce his army sufficiently to accomplish all these objects. On the same day a new military department was created called the Department of the Gulf, and Butler was assigned to the command. Its limits were to comprise all the coast of the Gulf of Mexico west of Pensacola harbor, and so much of the Gulf States as might be occupied by Butler's forces. Since the middle of October he had commanded the expeditionary forces, under the name of the Department of New England. Arriving at Ship Island on the 20th of March, he formally assumed the command of the Department of the Gulf, announcing Major George C. Strong as Assistant Adjutant-General and Chief of Staff, Lieutenant Godfrey Weitzel as Chief Engineer, and Surgeon Thomas Hewson Bache as Medical Director. To these were afterward added Colonel John Wilson Shaffer as Chief Quartermaster, Colonel John W. Turner as Chief Commissary, and Captain George A. Kensel as Acting Assistant Inspector-General and Chief of Artillery.