Colonial consolidation, the economic transformation it produced, and the movement that ended it.
The transition from Mughal successor states to Company rule, the structure and economics of colonial administration, the revolt of 1857, social and religious reform movements, and the national movement through to independence and partition.
Connecting cause to consequence across decades. Modern history has dense documentation, so the difficulty is not finding evidence but organising it — separating what changed structurally from what merely happened.
Drain of wealth, deindustrialisation, commercialisation of agriculture and famine policy run underneath the political narrative and explain much of it. Treating them as a separate topic rather than a connected thread is the usual mistake.