McClernand’s Corps, immediately upon debarking on April 30, headed for the bluffs 3 miles inland. By nightfall the Federal soldiers had reached the high ground and pushed on toward Port Gibson, 30 miles south of Vicksburg. From this point, roads led to Grand Gulf, Vicksburg, and Jackson. Maj. Gen. John S. Bowen moved his Grand Gulf command toward Port Gibson to intercept the threat, and, at daylight on May 1, leading elements of the Union advance clashed with Bowen’s troops, barring the two roads which led to Port Gibson. The battle of Port Gibson was a series of furious day-long engagements over thickly wooded ridges cut by deep, precipitous gullies and covered with dense undergrowth. While greatly outnumbering Bowen, McClernand was prevented by the rugged terrain from bringing his whole force into action. Slowly forced backward, Bowen conducted an orderly retreat through the town, which he evacuated. The holding action had cost Bowen 800 casualties from his command of 8,000; Union losses were about the same from a force at hand of about 23,000. Pemberton determined not to contest Grand Gulf lest he risk being cut off from Vicksburg and withdrew across the Big Black River. Thus he permitted Grant to occupy Grand Gulf and gave him a strong foothold on the east bank of the Mississippi. THE STRATEGY OF THE VICKSBURG CAMPAIGN. Grant’s overall strategy, up to the capture of Grand Gulf, had been first to secure a base on the river below Vicksburg and then to cooperate with Maj. Gen. Nathaniel P. Banks in capturing Port Hudson. After this he planned to move the combined force against Vicksburg. Port Hudson, a strong point on the Mississippi near Baton Rouge, was garrisoned by Confederate troops after Farragut’s withdrawal the previous summer. At Grand Gulf, Grant learned that Bank’s investment of Port Hudson would be delayed for some time. To follow his original plan would force postponement of the Vicksburg campaign for at least a month, giving Pemberton invaluable time to organize his defense and receive reinforcements. From this delay the Union Army could expect the addition of no more than 12,000 men. Grant now came to one of the most remarkable decisions of his military career.