By late August, the Parliamentarian cause was close to collapse but was saved by Pym's leadership and determination, which resulted in important reforms. Both sides struggled to properly supply troops fighting outside their home regions and Parliament agreed steps to mitigate the problem. Seeing an opportunity to force Parliamentary moderates into a negotiated peace, in September the Royalists agreed a new three-part offensive. After taking Gloucester, Prince Rupert would advance on London, while Newcastle would tied down the Eastern Association army by advancing into East Anglia and Lincolnshire. Finally, Hopton would march into Hampshire and Sussex, threatening London from the south, and closing the iron foundries that were Parliament's main source of armaments.