Kammala jumla mai zuwa: An nada Dowling a matsayin Knight Commander of the Order of the British Empire (KBE) a cikin Honours na Sabuwar Shekara ta 1957, kuma ya kammala aikinsa a matsayin CNS a ranar 23 ga Fabrairun 1959. A ranar 23 ga Maris ya maye gurbin Sir Henry Wells a matsayin Shugaban Kwamitin Shugabannin Sojoji (COSC), rawar da ke nuna cewa Babban Jami'in Tsaro. An maye gurbinsa a matsayin CNS ta Mataimakin Admiral Henry Burrell. Da farin ciki ya yi mamakin nadin sa a matsayin Shugaban COSC, Dowling ya yi fatan canza matsayin ta yadda zai yi amfani da ikon umarni a kan shugabannin sabis, amma a cikin wannan ya zama abin takaici. Matsayin matsayin ya kasance daidai da shugabannin Sojojin Ruwa, Sojojin Ruwa da Sojojin Sama, kuma kawai yana da alhakin gabatar da ra'ayoyinsu kan al'amuran soja ga Ministan Tsaro. Sauran abubuwan da suka faru a lokacin da yake aiki sun hada da shawarar Ma'aikatar Tsaro - wanda aka soke bayan wa'adinsa - don rushe rundunar Sojan Sama, da kuma gazawar gwamnatin Tarayya ta goyi bayansa lokacin da ya sanar a wani taron manema labarai na SEATO a watan Maris 1961 cewa Ostiraliya a shirye take ta shiga tsakani ta hanyar soja a cikin
rikicin Laos na biyu idan ya zama dole. A watan Satumbar 1959, a lokacin rikicin Laotian na farko, gwamnatin Ostiraliya ta ba Dowling izinin yin "battalion na sojan sama, rundunar mayakan RAAF, jigilar jiragen sama, da masu hallaka RAN guda biyu" don tallafawa sojojin Amurka da SEATO, amma babu wani tsoma baki da ya faru.