when two unobserved corps of the union army of the potomac, which combined with the union army of the james outside petersburg, failed to seize the city from a small force of confederate defenders at the second battle of petersburg, the 292-day richmond–petersburg campaign (siege of petersburg) began. union general-in-chief ulysses s. grant had to conduct a campaign of trench warfare and attrition in which the union forces tried to wear down the less numerous confederate army, destroy or cut off sources of supply and supply lines to petersburg and richmond and extend the defensive lines which the outnumbered and declining confederate force had to defend to the breaking point. after the battle of hatcher's run on february 5–7, 1865 extended the lines another , lee had few reserves after manning the lengthened defenses. lee then knew that part or all of his army must leave the richmond and petersburg lines, obtain food and supplies at danville, virginia or possibly lynchburg, virginia and join general joseph e. johnston's force opposing major general william t. sherman's army in north carolina. if the confederates could quickly defeat sherman, they might turn back to oppose grant before he could combine his forces with sherman's. lee began preparations for the movement and informed confederate president jefferson davis and confederate states secretary of war john c. breckinridge of his conclusions and plan.