Complex sentence: In the face of these catastrophes, Cassander sued for peace, but Antigonus rejected the claims, and Demetrius invaded Thessaly, where he and Cassander faced off against each other in inconclusive engagements.
Split into simpler sentences: In the face of these catastrophes, Cassander sued for peace, but Antigonus rejected the claims. Demetrius then invaded Thessaly, where he and Cassander faced off against each other in inconclusive engagements.