The following is what Longstreet himself had to say on the matter in his
From Manassas To Appomattox: This starts on page 326, when Longstreet is
en route from Suffolk back to Lee at Fredericksburg:
As soon as the trains were safely back, we drew off, marched back to the Blackwater, and thence en route for Richmond and Fredericksburg. Before we reached the former place a telegram came announcing the great battle and victory of Chancellorsville.
Passing through Richmond, I called to report to Secretary of War Seddon, who referred to affairs in Mississippi, stating that the department was trying to collect an army at Jackson, under General Joseph E. Johnston, sufficient to push Grant away from his circling lines about Vicksburg. He spoke of the difficulty of feeding as well as collecting an army of that magnitude in Mississippi, and asked my views.
The Union army under General Rosecrans was then facing the Confederate army under General Bragg in Tennessee, at Murfreesboro and Shelbyville.
I thought that General Grant had better facilities for collecting supplies and reinforcements on his new lines, and suggested that the only prospect of relieving Vicksburg that occurred to me was to send General Johnston and his troops about Jackson to reinforce General Bragg's army; at the same time the two divisions of my command, then marching to join General Lee, to the same point ; that the commands moving on converging lines could have rapid transit and be thrown in overwhelming numbers on Rosecrans before he could have help, break up his army, and march for Cincinnati and the Ohio River ; that Grant's was the only army that could be drawn to meet this move, and that the move must, therefore, relieve Vicksburg.
It was manifest before the war was accepted that the only way to equalize the contest was by skilful use of our interior lines, and this was so impressed by two years experience that it seemed time to force it upon the Richmond authorities. But foreign intervention was the ruling idea with the President, and he preferred that as the easiest solution of all problems.
The only objection offered by the Secretary was that Grant was such an obstinate fellow that he could only be induced to quit Vicksburg by terribly hard knocks. On the contrary, I claimed that he was a soldier, and would obey the calls of his government, but was not lightly to be driven from his purpose.
My march was continued, and we joined General Lee at Fredericksburg, where I found him in sadness, not withstanding that he was contemplating his great achievement and brilliant victory of Chancellorsville, for he had met with great loss as well as great gains. The battle had cost heavily of his army, but his grief was over the severe wounding of his great lieutenant, General Thomas Jonathan Jackson, the head of the Second Corps of the Army of Northern Virginia ; cut off, too, at a moment so much needed to finish his work in the battle so handsomely begun. With a brave heart, however, General Lee was getting his ranks together, and putting them in condition for other useful work.
...
After reporting to General Lee, I offered the suggestions made to Secretary Seddon, in regard to the means that should be adopted for the relief of Vicksburg. I thought that honor, interest, duty, and humanity called us to that service, and asked the aid of his counsels with the War Department, and reinforcements from his army for the West, to that end. I suggested that General Johnston, instead of trying to collect an army against General Grant, should be sent to reinforce General Bragg, then standing against the Union forces under General Rosecrans in Middle Tennessee ; that at the same time he should send my divisions, just up from Suffolk, to join Johnston's reinforcements to Bragg's army ; that the combination once made should strike immediately in over whelming force upon Rosecrans, and march for the Ohio River and Cincinnati.
He recognized the suggestion as of good combination, and giving strong assurance of success, but he was averse to having a part of his army so far beyond his reach. He reflected over the matter one or two days, and then fell upon the plan of invading the Northern soil, and so threatening Washington as to bring about the same hoped-for result. To that end he bent his energies.
His plan or wishes announced, it became useless and improper to offer suggestions leading to a different course. All that I could ask was that the policy of the campaign should be one of defensive tactics ; that we should work so as to force the enemy to attack us, in such good position as we might find in his own country, so well adapted to that purpose, which might assure us of a grand triumph. To this he readily assented as an important and material adjunct to his general plan. His confidence in making moves threatening Washington and the invasion of Maryland and Pennsylvania grew out of the known anxiety of the Washington authorities as to the safety of their capital and of quiet within the Union lines.