Complex sentence: In 1496, Bauck Poppema defended the fort pregnant during a siege of Groningen successfully until reinforcements arrived for the enemy, after which the fort fell and all her soldiers were executed.
Split into simpler sentences: In 1496, a pregnant Poppema successfully defended the fort for a time during a siege by invaders from the city of Groningen. Eventually, however, enemy reinforcements arrived, after which the fort fell and all of Poppema's soldiers were executed.