This study aims to highlight Oman's history from 1856 to 1868 during which time, Oman's influence started gradually disappearing from the Arabian Gulf and Fast Africa due to internal chaos and external influences. This caused to change the important role Oman played at that time and reduced its political and economical role that used to influence the region, and led to its economic recession This study relies on published and unpublished documents, sources and references relating to the period covered by the study, which used analytical descriptive method to study historical facts and to reach to the essence of historical events relevant to the study's subject The study is divided into, introduction, preface, four chapters and conclusion The preface deals with the internal events and external development that Oman went through during the reign of Imam Ahmed bin Said, which had an influence on the course of events in later periods that are covered by this study. The first chapter covers the era Oman went through since Sayyid Thuwaini bin Said ascended to the throne during the insistence of Sayyid Majid to severally rule Zanzibar with the support of the British authorities. The chapter also discusses the wish of Omani tribes at that time to get their independence, which was clear from their fighting against the ruling authority, and their unity to fight beside Sayyid Turky. The second chapter covers the internal challenges that Sayyid Salim bin Thuwaini faced after his father was killed, when his uncle disputed him on the throne, where the situation ended by the rise of Imamah presided by Azan bin Oals. Those events were interposed by emerging Wali of Musinah as a basic operator of Pani Hana'ah rebellions at that time. The third chapter of the study focuses on the policy followed by Britain dealing with Oman from 1856 to 1868, which relied on Britain ensuring its expansion plans were successful and on finding an outlet in Arabian Gulf and East Africa The fourth chapter deals with Oman's relationship with competitive regional powers at that period, that is Saudi state and Persia. It also shows the persistent Saudi intervention in Oman's internal affairs and Saudi's attempts to control some parts of Omani lands. It also deals with the Persian stance of the Omani hegemony on its costs and Persia's operation resisting that hegemony in preparation to end Oman's control of its lands on its coasts. The study is concluded by stating the outcome of all the situations covered in it. This can be summarized in the negative impact created by Sayyid Said bin Sultan moving to Zanzibar resulting in Omani tribes having a better influence. This eventually had a clear role in changing the internal course of events in Oman which allowed Sadi intervention in Omani internal affairs to gain Omani tribes loyalty. Persis also got benefited from that situation to get rid of Omani control of parts of its land. During that period, Britain played the role of solving conflict of interest between those parties, whilst taking advantage of the situation for its own benefits.