Complex sentence: In 1119, Genoese assaulted some Pisan galleys, beginning a bloody war, fought on sea and land, that lasted till 1133 interrupted by several truces that were sometimes observed and sometimes violated.
Split into simpler sentences: In 1119, the Genoese attacked some Pisan galleys, beginning a bloody war on sea and land. It lasted until 1133, interrupted by several truces that were sometimes observed and sometimes violated.