Byzantine retreat in Bithynia

Timeline

1. 1290–1295Bithynian frontier · BithyniaTurkic beyliks and Mongol vassal forces raided continuously; Byzantine garrisons along the Nicaea–Bursa line were undermanned and short of supplies, leaving many frontier positions isolated.
2. 1296–1299Bithynian hinterland · BithyniaImperial military and civil authorities pulled back to the Marmara coast and a few major towns; inland fortresses fell or were abandoned in succession, and Bithynia's hinterland effectively slipped from effective Byzantine rule.