As tribal protection did not extend to slaves and the mawali, the Quraysh turned from social pressure to outright torture of the weak. Abu Jahal, whom the Prophet ﷺ called the fir'awn (Pharaoh) of this ummah, led the campaign and graded his cruelty by class: converts among the Quraysh nobility faced verbal abuse, those who did business with the Quraysh were boycotted, and slaves and mawali, who had no tribe to protect them, were tortured outright.
Ibn Abbas later recounted to his student Sa'id ibn Jubayr that the believers were tortured, starved, and deprived of water so severely that they could not even sit up from the pain. It reached the point that when asked, "Is al-Lat and al-Uzza your god?" they would answer, "Yes", and even that if an insect passed by them and they were told to call it their god, they would do so. This is permissible in Islam when said under torture, so long as the heart remains firm in faith.
The first seven to publicly declare Islam (the Prophet ﷺ, Abu Bakr, Ammar ibn Yasir, Sumayyah, Suhayb al-Rumi, Bilal ibn Rabah, and al-Miqdad) were rounded up by the Quraysh. Only the Prophet ﷺ and Abu Bakr were shielded, through Abu Talib and Abu Bakr's own tribe respectively, while the rest were tortured with irons and left in the desert sand.