Rubuta ci gaba ga wannan sakin layi - Callaghan ya zama kwamandan kwamandan jirgin ruwa kuma ya umurce shi a cikin motsa jiki a lokacin rani na 1901 kafin ya zama kwamandan kwamandan jirgin ruwa a kan tashar Rumunan a watan Disamba na 1901. Ya ci gaba da zama Kyaftin na Portsmouth Dockyard a farkon 1904 kuma kwamandan kwamandan jirgin ruwa a kan tashar Rumunan bayan haka. An nada shi mataimakin mai kula da jirgin ruwa ga Sarki a ranar 25 ga Afrilu, 1904. An ba shi mukamin Admiral a ranar 1 ga Yuli, 1905, ya zama na biyu a cikin Kwamandan, Channel Fleet, tare da tutar sa a cikin jirgin ruwa, a cikin 1906 da kwamandan rundunar sojan ruwa ta 5th, tare da tutar sa a cikin jirgin ruwa mai sulke, a cikin 1907. An nada shi Kwamandan Royal Victorian Order a ranar 3 ga Agusta 1907, ya ci gaba da zama na biyu a cikin Kwamandan Jirgin Ruwa na Bahar Rum tare da tutar sa a cikin jirgin ruwa a 1908. A wannan matsayi na karshe ya taimaka tare da samar da taimako ga wadanda suka tsira daga girgizar kasa na Messina.
, wanda ya haifar da asarar rayukan mutane 123,000, a watan Disamba na shekarar 1908, wanda aka inganta shi zuwa Knight Commander na Royal Victorian Order a ranar 30 ga Afrilu 1909 kuma aka nada shi Babban Jami'in Dokar Sarautar Italiya a ranar 15 ga Afrilu 1912. An ci gaba da zama mataimakin mataimakin shugaban kasa a ranar 27 ga Afrilu, 1910, ya zama na biyu a cikin kwamandan rundunar jiragen ruwa na gida, tare da tutar sa a cikin jirgin yaƙi daga baya a wannan watan. An ci gaba da shi zuwa Knight Commander na Order of Bath a ranar 24 ga Yuni, 1910.