Complex sentence: This situation eventually led to the massacre of major Pietro Toselli's column, that, isolated in an outpost on Amba Alagi, never received the orders to retreat and was trapped by the advancing army of Menelik.
Split into simpler sentences: This situation eventually led to the massacre of Major Pietro Toselli's column. Isolated in an outpost at Amba Alagi, Toselli never received the orders to retreat and was trapped by the advancing army of Menelik.