Two short ones:
1) “This is because the 13th-century Italy was unusual.”
“This is because 13th-century Italy was unusual.”
Drop the definite article when you use AS A NOUN PHRASE “13th-century Italy” or “19th-century France” or “x-th-century whatever.”
2) “In the 13th century…” – no hyphen.
“In 13th-century Italy…” – hyphen.
In other words, hyphenate “13th-century” if you use it adjectivally (admittedly, not all editors follow this rule. In any case, be consistent. If you hyphenate on page four, also hyphenate on page 31 of your essay).
DO NOT hyphenate “In the 13th century…”
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