Complex sentence: During her medical training Laura joined the British Army, and served for ten years both in the NHS and overseas as an army medical officer reaching the rank of major until she was medically retired in 2014 due to developing epilepsy.
Split into simpler sentences: During her medical training Laura joined the British Army, and served for ten years both in the NHS and overseas as an army medical officer. Eventually after reaching the rank of major she was medically retired in 2014 due to developing epilepsy.