As the Japanese regrouped west of the Matanikau , the U.S. forces concentrated on shoring up and strengthening their Lunga defenses . On 14 September , Vandegrift moved another battalion , the 3rd Battalion , 2nd Marine Regiment ( 3 / 2 ) , from Tulagi to Guadalcanal . On 18 September , an Allied naval convoy delivered 4 @,@ 157 men from the 3rd Provisional Marine Brigade ( the U.S. 7th Marine Regiment augmented by additional support units ) to Guadalcanal . These reinforcements allowed Vandegrift — beginning on 19 September — to establish an unbroken line of defense around the Lunga perimeter . Vandegrift 's forces ' next significant clashes with the Japanese occurred along the Matanikau River from 23 – 27 September and 6 – 9 October .