The Combined Fleet was re-formed during the Russo-Japanese War of 1904–05 to provide a unified overall command for the three separate fleets in the Imperial Japanese Navy. The IJN 1st Fleet was the main battleship force, which formed the backbone of the navy and was intended to be used in a traditional line-of-battle showdown with an equivalent enemy battleship fleet ("kantai kessen"). The IJN 2nd Fleet was a fast, mobile strike force with armored cruisers and protected cruisers. The IJN 3rd Fleet was primarily a reserve fleet of obsolete vessels considered too weak for front-line combat service, but which could still be used in the operation to blockade Port Arthur. Admiral Tōgō Heihachirō was commander-in-chief of the Combined Fleet during the Russo-Japanese War.