In the Battle of Sekigahara in 1600, he was assigned to lead a detached force going through the Nakasen-do Road and planned to arrive at Akasaka-shuku Post station town in Mino Province on October 16 (The Fukushima family document mentioned 'Chunagon is to arrive at the place around the tenth'), while the main force led by Ieyasu was going through the Tokai-do Road.
慶長5年（1600年）の関ヶ原の戦いでは、東海道を進む家康本隊に対して、中山道を進む別働隊を率いる役割を与えられ、9月10日に美濃の赤坂宿に到着する予定（福島家文書に「中納言、さだめて十日時分には其地まで参るべし」）だった。