Complex sentence: Tynan was twelve at the outbreak of the Second World War and at thirteen came close to being killed when a landmine destroyed the houses on the other side of the Birmingham street where the Tynans lived, killing the inhabitants.
Split into simpler sentences: Tynan was twelve at the outbreak of the Second World War. At thirteen, he was nearly killed when a landmine destroyed the houses on the other side of the Birmingham street where the Tynans lived, killing the inhabitants.