Let us pause a moment, for the purpose of narrating the movements of the Confederate army, which had caused this sudden departure of ours into Maryland. After the check given to Gen. Jackson at Chantilly, Gen. Lee decided to invade Maryland. He hoped by this action to have his army largely recruited from the great number of Southern sympathizers in that State, whom it had been said were only waiting for just such an opportunity as this would give them, to join the Confederate army. Gen. Jackson was ordered to march for the Potomac, and between the 4th and 5th of Sept. the whole Confederate army had crossed into Maryland, and was encamped near Frederick, on the Monocacy River. Gen. Lee issued an address to the people of Maryland, inviting those who were in sympathy with the Southern cause, to join the army; but it fell flat, and he lost more by desertions than he gained by recruits from the Marylanders. On the 9th of Sept. Gen. Lee issued Special Order No. 119, in which he ordered Gen. Jackson to proceed to Harper's Ferry, and oblige its surrender. Gen. Longstreet and the rest of the army were ordered to proceed to Boonsboro,—thus his army was divided. Happily this order fell into the hands of Gen. McClellan, who acted upon its information immediately by following the main part of the Confederate army, attacking it and driving it over South Mountain down to Antietam, and it was late in the afternoon of the 17th before Lee's army was fully united.

The morning of the 15th saw Battery D upon the road again, and by noon we had reached the summit of South Mountain. As we passed along we saw numerous evidences of the severe struggle. Many of the dead, both of our own and the rebel forces, lay by the roadside and in the fields, burial parties being then at work digging graves.

During the afternoon we continued our winding way down the mountain, following the pike road which led through the village of Boonsboro, and went into camp just beyond the village. On the morning of the 16th we were hitched up and ready to move, but did not get the order to move until about noon; when, passing through Keedysville, we followed the pike until near McClellan's head-quarters, the vicinity of which we reached just before dark, and turning to the right crossed Antietam Creek, and after marching for sometime in a somewhat circuitous route went into park about nine o'clock, with a number of other batteries. Our position was on cleared ground and on the summit of a commanding ridge, as we discovered next morning.

As our infantry advanced to establish a picket line, they were met with a heavy fire, which convinced us that the enemy were in our near presence, and in large force. Their artillery shelled us continually, and the flight of the shells with their burning fuses, together with the flash of the small arms, made a very pretty display, but we were all glad when the exhibition came to a close, just before ten o'clock.

The teams were not unhitched, but the bridles were dropped, giving the horses an opportunity to feed. It was late before the horses were fed and the men had eaten their suppers, but finally all had disposed themselves for sleep, either upon the ground, or on the chests of the caissons, and were soon utterly indifferent to their surroundings and the prospects of trouble on the morrow.

Just at daylight the next morning we were awakened by a shell that went screeching over the battery, and in a minute or two it was followed by quite a lively lot of them, but their elevation was just a little too high, and they passed over us, only one doing any damage.

Cannoniers rushed to their posts, drivers to their horses: bridles were hastily slipped on, and in less time than it takes to tell it, were executing the movement "Action front," in answer to an order from the Captain. As the men succeeded in rubbing their eyes open, and recovered from their astonishment, they looked about for an explanation of this disturbance. It was in the gray of dawn, and the few first rays of the rising sun had made it possible for us to see the surrounding hills. From one of these a battery or two of rebels had discovered our position, and gotten in the first blow; but they had no idea what a hornets' nest they were stirring up, for it so happened that upon that ridge there lay four batteries: upon our left lay Battery B, Fourth United States, upon our rear Battery L, First New York, and the First New Hampshire, and as quickly as possible every gun, twenty-four in number, was firing in reply to the enemy.

Capt. Monroe says of this part of the action:

"I have always thought that but one battery opened upon us, though others believe there were two or three opposed to us. Whatever number there was, they must have found their position a warm one, for the gunners of three of these (our batteries) could not be excelled for marksmanship, estimation of distances, and all the good qualities which go to make a skillful gunner. The previous winter they had been exercised by Capt. Gibbon in firing at target, sighting, etc., and they had acquired great proficiency in these points. The fuses of the shell and case were accurately timed, and the projectiles burst where it was intended they should, among the guns and limbers of the enemy, who had stirred up a hornets' nest, and the hornets proved too many for him."

After the rebel battery had retired, and the firing ceased, the men of Battery D had an opportunity to look about them, take in the lay of the land, etc. In our front the ground sloped gradually for several hundred yards, at which distance it was crossed at nearly right angles with our position by a sunken road, in which the rebel line of battle was posted.