On the 14th of April he penned this brief telegram to Banks:
"I am concentrating my forces at Grand Gulf; will send an army corps Bayou Sara by the 25th, to co-operate with you on Port Hudson. Can you aid me and send troops after the reduction of Port Hudson to assist me at Vicksburg?"
This message, although Banks and Grant were then only about two hundred miles apart, had to travel three thousand miles to reach its destination. Banks received it just before marching from Opelousas on the 5th of May, twenty-one days after it left Grant's hands. As received, the message was in cipher and without a date. As the prevailing practice was, in conformity with the orders of the Secretary of War, the only persons in the Department of the Gulf who held the key to the cipher were the Superintendent of Military Telegraphs and such of his assistants as he chose to trust, and Mr. Bulkley was at New Iberia, where the wires ended. The code employed was the route cipher in common use in the service, and with the help of the words "Bayou" and "Sara" as guides the meaning was not hard to make out. Banks did not trust to this, however, and waited until, late at night, he received from the Superintendent an official translation, still without date, as indeed was the original document received at headquarters from New Orleans. The 25th Banks naturally took to mean the 25th of May. Grasping eagerly at the first real chance of effective co-operation, he at once replied: "By the 25th probably, by the 1st, certainly, I will be there." This despatch was not in cipher, because he had no code. Captain Crosby carried it to the _Hartford_ at the mouth of Red River. Captain Palmer, who was found in command, the Admiral having crossed Fausse Point and joined his fleet below, at once forwarded the despatch. Near Natchez Crosby met Captain Uffers of Grant's staff and turned back with him bringing Grant's despatch of the 10th of May, written at Rocky Springs. This Banks received at Alexandria on the 12th of May. From it he learned that Grant was not coming. Having met the Confederates after landing at Grand Gulf and followed on their heels to the Big Black, he could not afford to retrace his steps; but he urged Banks to join him or to send all the force he could spare "to co-operate in the great struggle for opening the Mississippi River." The reasons thus assigned by Grant for his change of mind were certainly valid; yet it must be doubted whether in these hurried lines the whole of the matter is set forth, for three weeks earlier, on the 19th of April, five days after the promise to send an army corps to Bayou Sara by the 25th, Grant had reported to Halleck: "This will now be impossible." Moreover, until the moment when he crossed the river with his advance on the 30th of April he not only held firmly to his intention to send the twenty thousand men to join Banks at Bayou Sara as soon as the landing should have been secured, but the corps for this service had been designated; it was to be made up of the main body of McClernand's corps and McPherson's, and Grant himself meant to go with it. It was indeed the 2d of May when Grant received at Port Gibson Banks's despatch sent from Brashear on the 10th of April indicating his purpose of returning to Baton Rouge by the 10th of May, and although Grant also attributes to this despatch the change of his plans, the 10th of May had already come before he made known the change to Banks.