Complex sentence: He attended Staff College at Camberley in 1897 as the first former ranker to go there and was then seconded for service in the Intelligence Department at the War Office on 1 April 1899.
Split into simpler sentences: He attended Staff College at Camberley in 1897 as the first former ranker to go there. He was then seconded for service in the Intelligence Department at the War Office on 1 April 1899.