The Japanese worked intensely for nearly a year to fortify the island. To aid the garrison in the construction of the defenses, the 1,247 men of the 111th Pioneers, similar to the Seabees of the U.S. Navy, along with the 970 men of the Fourth Fleet's construction battalion, were brought in. Approximately 1,200 of the men in these two groups were Korean laborers. The garrison itself was made up of forces of the Imperial Japanese Navy. The Special Naval Landing Force was the marine component of the IJN, and were known by U.S. intelligence to be more highly trained, better disciplined, more tenacious and to have better small unit leadership than comparable units of the Imperial Japanese Army. The 3rd Special Base Defense Force assigned to Tarawa had a strength of 1,112 men. They were reinforced by the 7th Sasebo Special Naval Landing Force, with a strength of 1,497 men. It was commanded by Commander Takeo Sugai. This unit was bolstered by 14 Type 95 light tanks under the command of Ensign Ohtani.