Armbruster was a pupil at Brighton College (School House) from 1911-1912. There are no records of particular accomplishments in the school records and given the fact that he spent only a year at the school and his age (18) when he started it is probable that he spent a year at Brighton College after leaving school in France with the intention of learning English. If he intended to follow in the footsteps of his father into the management of one of the premier hotels in Paris then fluent English would presumably have been a useful skill.
After he left Brighton College it seems likely that he was conscripted to straight into the French army to do compulsory military service as all young Frenchmen were obliged to do. In 1913 the length of conscription was increased in France was, very controversially, increased to three years and those who were already serving, such as Armbruster, were expected to spend another year with the colours. On the outbreak of war, therefore, it is likely that Armbruster had already been a serving soldier with his regiment, the 13e R.I. Régiment d’Infanterie, for over two years.