Complex sentence: Construction started in 1283 as part of Edward I's second Welsh campaign, the castle was part of Edward's iron ring of castles around Snowdonia, a string of new castles to hem the prince in.
Split into simpler sentences: Construction started in 1283 as part of Edward I's second Welsh campaign. The castle was part of Edward's iron ring of castles around Snowdonia, a string of new castles to hem the prince in.