B. R Ambedkar's role and contribution to the making of the Indian Consitution is certainly of the most significant level-- on 15th August 1947, when India achieved its independence, Nehruji made Ambedkar as his first Law Minister, in recognition of his legal prowess; and also, in fact, made him the Chairman of the Indian Constitution Drafting Committee: a singular honour, and of course, his first/primary important 'contribution' to this document i.e. its actual writing/drafting and structuring, which is no small thing, as it is Ambedkar ji's words that roll off so decorously when we read the document.
As writer/drafter/framer and 'prime mover' of the new Indian Constitution, Ambedkar also had a central role in guiding his committee towards the sort of socialistic, idealistic vision that he had, and that to some extent he also shared with Nehru ji. According to Granville Austin, this document thus was first and foremost, a 'social document' i.e. one which identified many of the basic problems besetting and needing to be addressed, for the amelioration of the masses-- and in this regard it is worthwhile noting down pointwise some of Ambedkar's main, personal contributions, depending upon his own expertise and interests/concerns:
1. Guarantees of basic civil liberties to Indian citizens
2. Abolition of all forms of discrimination of caste and creed, freedom of religion and abolition of 'untouchability' in principle at least-- something very peronal for him, coming as he did from untouchable origins.
3. Equal rights under law to Indian women, and full social and economic freedom/s to them, too.
4. Various job quotas guarantees for scheduled castes and tribes and minorities in India, to ensure fairplay and some modicum of 'removal' of social inequalities for remote and underpriviliged communities.
These were no small achievements personally, and along with their adoption, the whole of the Indian Constitution was thereafter formally passed by Parliament (Constituent Assembly) on 26th November 1949.
another history question masquerading as law now!