Exploiting this flaw in the Sui system, Yodong and other citadels of Goguryeo continued to hold on; by June, five months after the beginning of the campaign, not a single fortress had fallen to Sui.
Yodong and other citadels of Goguryeo were exploiting this flaw in the Sui system. Yodong and other citadels of Goguryeo continued to hold on. Not a single fortress had fallen to Sui. This was five months after the beginning of the campaign. This was by June.