Complex sentence: In 1372 Owain Lawgoch a claimant to the Welsh throne, at the head of a free company, on behalf of France, attacked Guernsey, popularly called "La Descente des Aragousais".
Split into simpler sentences: In 1372 Owain Lawgoch, a claimant to the Welsh throne, attacked Guernsey at the head of a free company, on behalf of France. This event is popularly called "La Descente des Aragousais".