Ahistorical public school bullshit. There have been passports as long as there has been writing. The first US passports were issued during the revolution. Post WWI there were understandably more controls between European borders than immediately before WWI but passports have existed throughout civilization from time immemorial.
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"Passe porte" in medieval times were issued to some to waive entry fees a city ports, enetring territories just required a fee. Passports and border controls were enforced after WWI. ๐ค๐ป
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As if there were infiltrators abound in the past.
Photo from 1900
From inside the Hijaz train, which used to connect Istanbul to the Hijaz, passing through Syria, Palestine and Jordan.. In the picture there are passengers from the Levant, Iraq, Mount Lebanon and Turkey
They all ride on the same train without visas, passports, or even an identity card.
They move between the ancient cities of the Levant to Jerusalem, then continue the road to the oases of Jordan, to reach the deserts of Hijaz, Mecca and Medina, as if they were on a bus transporting them from one neighborhood to another within one city.

It was after WWI that a International standard was created. Yes there were citizenship documents before, but nothing at the same scale.