The rank and file of the armies found themselves, with increasing frequency, living inside entrenchments just a few yards away from their enemies. Restless and creative men in both armies plotted ways to blow each other up. The classic example of that phase is the Battle of the Crater, southeast of Petersburg in July 1864, where Union soldiers excavated a long tunnel and exploded a portion of the Confederate line. It did not prove effective, and the post-explosion combat ended in a decisive Union defeat.
An aborted tunnel at Cold Harbor is less well known, though of greater interest to Richmond National Battlefield Park. It predated the Crater by more than one month. The course of the battle at Cold Harbor and some favorable geography combined to provide the perfect opportunity for underground mischief. Relative quiet followed the bitter fighting on June 3, 1864. Field entrenchments grew powerful. General Winfield S. Hancock’s Second Corps occupied earthen fortifications downslope from Confederate defenses that snaked across a hilltop. The respective skirmishers at that spot, each offering a protective buffer for their primary line, lay so close that bored men occasionally hurled pieces of hard bread across the intervening yards in an outdoor food fight.
After a day or two of that the Union soldiers began excavating a tunnel into the steep eastern face of the Confederate-held hill. They hoped to build an underground gallery deep enough into the slope to reach beneath the Confederate position. If everything went perfectly, they could ignite a massive explosion, breach a hole in the entrenchments, and take advantage of the ensuing surprise to unravel the defenders. Before the work had progressed far, Ulysses Grant disengaged the Federal army and moved off toward the James River. His men had to abandon the unfinished tunnel. Given a little more time, the Battle of the Crater could well have occurred at Cold Harbor in June rather than at Petersburg in July.