HDQRS. MILITARY DIVISION OF THE MISSISSIPPI,
In the Field, near Chattahoochee River, July 12, 1864.

Lieutenant-General GRANT, Near Petersburg, Va.:

DEAR GENERAL: I have written you but once since the opening of the campaign, but I report by telegraph to Halleck daily, and he furnishes you copy. My progress was slower than I calculated, from two chief causes, an uninterrupted rain from June 2 to about the 22d, and the peculiar sub-mountainous character of the country from the Etowah to the Chattahoochee. But we have overcome all opposition and whipped Johnston in every fight where we were on anything like fair terms, and I think the army feels that way, that we can whip the enemy in anything like a fair fight, but he has uniformly taken shelter behind parallels of strong profile made in advance for him by negroes and militia.

I regarded an assault on the 27th of June necessary for two good reasons; first, because the enemy as well as my own army had settled down into the belief that flanking alone was my game; and second, that on that day and ground, had the assault succeeded, I could have broken Johnston's center and pushed his army back in confusion, and with great loss to his bridges over the Chattahoochee. We lost nothing in morale by the assault, for I followed it up on the extreme right and compelled him to quit the very strong lines of Kenesaw, Smyrna Camp, and the Chattahoochee in quick succession.

My railroad and telegraph are now up and we are rapidly accumulating stores in Marietta and Allatoona that will make us less timid about the roads to our rear.

We have been wonderfully supplied in provisions and ammunition; not a day has a regiment been without bread and essentials. Forage has been the hardest, and we have cleaned the country in a breadth of thirty miles of grain and grass. Now the corn is getting a size which make a good fodder, and the railroad has brought us grain to the extent of four pounds per animal per day.

I have now fulfilled the first part of the grand plan. Our lines are up to the Chattahoochee, and the enemy is beyond. Morgan failed in his Kentucky raid, and we have kept Forrest employed in Mississippi. The defeat of Sturgis was unfortunate; still, he kept Forrest away from us; and now A. J. Smith is out with a force amply sufficient to whip him. I hear of Slocum at Jackson, Miss., and Camby telegraphs me of a trip from Baton Rouge and another against Mobile, so that I am well satisfied that all my people are well employed. At this moment I have stoneman down the Chattahoochee, with orders, if possible, to cross and strike the West Point road; and Rousseau left Decatur the 8th instant, with about 3,000 cavalry and no wagons, with orders to make a bold push for the railroad between Montgomery and West Point and break it good; to return to the Tennessee, if possible, but if headed off to make for Pensacola. The moment I got Johnston to the Chattahoochee I sent Schofield to a ford above, and he effected a crossing without the loss of a man, and has two pontoon bridges. About the same time, Garrard's cavalry crossed, still above, at Roswell Factory, and has been relieved by Dodge's corps, so that I now cover the Chattahoochee and have two good crossings well secured; by to-night I will have a third.

As soon as I hear from Stoneman I will shift all of McPherson to Roswell and cross Thomas about three miles above the railroad bridge and move against Atlanta, my left well to the east, to get possession of the Augusta road about Decatur or Stone Mountain. I think all will be ready in three days. I will have nearly 100,000 men.