CK3 Bulgaria in 867 inherited the faulty cut down map from CK2. Plovdiv (Philippopolis) was inside Bulgaria for a century at that Point and Beroe province (Zagore province) was inside BG borders since ca 700 AD. The Rhodope mountains provinces (Rhodope and Zherkovo) were also inside the borders, as was Philippi at the Aegean coast. More @Wikipedia
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