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The Blocksize War

3 min read

Summary

The definitive account of the 2015–2017 conflict over Bitcoin’s block size limit. Bier is a Bitcoin researcher who documented the conflict in real time; this book is a chronological, detailed history of every major event in the war. Available also as an audiobook.

The blocksize war is the most important governance event in Bitcoin’s history: it determined whether miners or full node operators controlled Bitcoin’s rules. Small blockers won.

Structure (21 chapters)

  1. First Strike — the initial salvo in the block size debate
  2. Beginning — origins of the disagreement
  3. Scaling Bitcoin I: Montreal — first conference (2015)
  4. Scaling Bitcoin II: Hong Kong — second conference
  5. SegWit — the proposed soft fork solution
  6. Lightning Network — the Layer 2 proposal
  7. Bitcoin Classic — the 2MB hard fork attempt
  8. Hong Kong Roundtable — the secret meeting where miners agreed to a hard fork, then reneged
  9. Fake Satoshi — Craig Wright’s false claim to be Satoshi; his alignment with large blockers
  10. DAO — Ethereum’s DAO hack and hard fork; contrast with Bitcoin’s approach
  11. Scaling Bitcoin III: Milan
  12. Bitcoin Unlimited — the next hard fork attempt
  13. Exchanges — how exchanges positioned themselves
  14. ASICBoost — Bitmain’s covert mining optimization; why they blocked SegWit
  15. Dragon’s Den — the closed meeting of large blockers
  16. Litecoin — SegWit activates on Litecoin first as a test
  17. UASF — User Activated Soft Fork; the user counter-attack
  18. New York Agreement — 58 companies sign SegWit + 2MB commitment
  19. Bitcoin Cash — the hard fork chain that Roger Ver and Jihan Wu launch August 1, 2017
  20. SegWit2x — the second part of the NYA; its eventual collapse
  21. Victory — SegWit activates; SegWit2x cancelled; small blockers win

Key Takeaways

Miners don’t control Bitcoin: Despite controlling hash rate and producing blocks, miners could not force a hard fork. Full node operators and the economic majority determined the outcome.

ASICBoost explains everything: Bitmain’s covert mining optimization was incompatible with SegWit. Their opposition to SegWit was not principled — it was economic self-interest. Once exposed, their credibility collapsed.

UASF was the decisive move: The threat of full node operators enforcing SegWit regardless of miner signaling changed the game. Miners faced losing all their revenue if they mined blocks the economic majority rejected.

Craig Wright’s involvement: His fraudulent Satoshi claim and alignment with large blockers damaged that side’s credibility. The book documents his behavior in detail.

The New York Agreement collapsed: 58 companies signed, but without Bitcoin Core developers, without full node operators, and without the economic majority, the agreement was meaningless. SegWit2x was cancelled by email to signatories, essentially admitting they had overestimated their power.

Why It Matters Today

The blocksize war set the template for Bitcoin governance: soft forks are the path of least resistance; hard forks require genuine network-wide consensus; full nodes are supreme. This template is now part of Bitcoin culture. Any future attempts to change Bitcoin’s fundamental rules will face the same resistance — including attempts to raise the 21M cap.

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