Complex sentence: At the outbreak of the Balkan Wars in September 1912, he joined the military and as it was one of the earliest conflicts where air-power was used, he concentrated on developing his aircraft towards becoming a decisive weapon.
Split into simpler sentences: At the outbreak of the Balkan Wars in September 1912 he joined the military. This was one of the earliest conflicts where air-power was used, he concentrated on developing his aircraft towards becoming a decisive weapon.