Oak Grove was the first of the Seven Days’ battles. On June 25, Maj. Gen. George B. McClellan advanced his lines along the Williamsburg Road with the objective of bringing Richmond within range of his siege guns. Union forces attacked over swampy ground with inconclusive results, and darkness halted the fighting. McClellan’s attack was not strong enough to derail the Confederate offensive that already had been set in motion. The next day, Lee seized the initiative by attacking at Beaver Dam Creek north of the Chickahominy.