While with the famed 1st Marine Division his duties were varied. While commander of the 2nd Battalion of 7th Marine Regiment during the Guadalcanal campaign he was awarded the Silver Star for conspicuous gallantry and intrepidity in action against the enemy. Hanneken relieved Colonel Julian N. Frisbie as commanding officer of the 7th Marines and led this regiment during the Peleliu action, where he received the Legion of Merit for meritorious conduct in action, and during the Cape Gloucester operation he was decorated with the Bronze Star.