Complex sentence: In 1198, Maud held off a massive Welsh attack led by Gwenwynwyn, Prince of Powys, against Pains Castle in Elfael, for three weeks until reinforcements arrived.
Split into simpler sentences: In 1198, Maud defended Pains Castle in Elfael against a massive Welsh attack led by Gwenwynwyn, Prince of Powys. She successfully held off Gwenwynwyn's forces for three weeks until reinforcements arrived.