Who violated the Treaty of Hudaybiyyah: was it the Muslims or Quraysh?

The Prophet (peace and blessings of Allah be upon him) set out in the year of Al-Hudaybiyyah intending 'Umrah, but Quraish prevented him from entering Makkah. A peace treaty was then concluded between them based on certain conditions, including: a ten-year cessation of hostilities; if anyone from Quraish came to the Muslims, they were to be returned; if anyone from the Muslims came to Quraish, they were not obligated to return him; the Prophet (peace and blessings of Allah be upon him) would return that year and come the following year for 'Umrah; and whoever wished to enter into an alliance with either party could do so.

Thus, the tribe of Khuza'ah entered into alliance with the Prophet (peace and blessings of Allah be upon him), and Banu Bakr entered into alliance with Quraish. Then Banu Bakr betrayed Khuza'ah, and Quraish aided them with weapons and combat, which constituted a breach of the Treaty of Al-Hudaybiyyah. Abu Sufyan attempted to renew the treaty but failed. The Prophet (peace and blessings of Allah be upon him) then prepared his army for the conquest of Makkah.