Group solidarity, not physique, makes Sikhs and Muslims fearless in danger.

Evidence

The question naturally arises: From where does the Sikh or the Mahomedan derive his strength, which makes him brave and fearless? I am sure it is not due to relative superiority of physical strength, diet or drill. It is due to the strength arising out of the feeling that all Sikhs will come to the rescue of a Sikh when he is in danger, and that all Mahomedans will rush to save a Muslim if he is attacked. — Ambedkar, B R, Annihilation of Caste_ The Annotated…, 893