Complex sentence: On 5 December 1928 Fortin Vanguardia, an advance outpost established by the Bolivian army a few miles northwest of Bahía Negra, was overrun by a Paraguayan cavalry unit, which captured 21 Bolivian soldiers and burnt the scattered huts to the ground.
Split into simpler sentences: On 5 December 1928 a Paraguayan cavalry unit overran Fortin Vanguardia, an advance outpost established by the Bolivian army a few miles northwest of Bahía Negra. The Paraguayans captured 21 Bolivian soldiers and burnt the scattered huts to the ground.