As previously reported, Gavin Andresen proposed increasing the block size and later attempted to describe the economic and political implications of such a proposal. In both instances he was met with furious backlash from the community.

Today Gavin posted on his personal blog an article titled "Looking before the Scaling Up Leap", stating "My goal is to prove that it is safe to raise the maximum block size from 1MB to at least 20MB" along with "I'll argue we should schedule a hard fork." Reddit soon blindly praised Gavin for his work, with comments such as "Fork it hard."

It appears as if Gavin will not give up unless his hard fork is a reality, and thus Mircea Popescu has made a declaration of war if Gavin proceeds with his plans.

There have only ever been two hard forks of the blockchain in the history of Bitcoin, and both nearly killed Bitcoin. The first was overseen by Satoshi in an attempt to fix the worst Bitcoin bug seen to date, and an unforeseen fork in which BerkeleyDB was replaced with LevelDB to allow for blocks greater than 512kb to be accepted by the network. The latter fork however didn't disenfranchise older clients by forcing them to use LevelDB over BerkeleyDB – a one line workaround resolves the bug in clients still running with BerkeleyDB.

Gavin's proposed fork will create a blockchain incompatible with any previous version of Bitcoin. Nodes who do not wish to upgrade will reject the larger blocks, while continuing to accept blocks on their own chain. Many don't seem to yet understand the implications of a Bitcoin hard fork this late in the protocol's maturity so let us ponder the consequences for a moment.

Gavin proposes the fork would not occur until one of his new gigablocks is mined, this block would denote the start of the fork. At this point full nodes refusing to run Gavin's patches will reject this larger block, while those sided with Gavin will accept the larger block – two block chains will begin to emerge. Unlike previous forks where political consensus was achieved, this fork is guaranteed to result in conflict – the Great Blockchain Civil War starts. MPEx and others will refuse to accept any outputs contained in the Giga-blockchain, MPEx will also begin to actively attack it:

mircea_popescu: ben_vulpes if one block's large and the other small, all i need a tx that's included in the large block but not the small one. then doublespend it on the small one, which will be rejected necessarily by the large block blockchain mircea_popescu: now i have bitcoin separated in two addresses, one for each chain. mircea_popescu: the attempt may fail, but the cost to me of this failure is not significant, so i can keep on trying until it succeeds. mircea_popescu: the only way to guard against it is, obviously,for the ."large" chain to maintain 1:1 identity with the "small" one. because you don't just fork bitcoin., ben_vulpes: i still fail to see how you're going to make a txn that gets included in the large block chain and not the small block chain. artifexd: ben_vulpes: You don't. You keep sending money to yourself until it happens. mircea_popescu: ben_vulpes what do you mean ? it necessarily will occur. mircea_popescu: since one contains more txn than the other by definition. mircea_popescu: suppose i make 50k 1btc txn. they don't fit in a 1mn block. they do fit in a 10mb block. what now ?

As the Giga-blockchain and main-blockchain continue to grow from the fork, those actively attacking the Giga-Blockchain will create many transactions that allow their main-blockchain coins to duplicate over to the Giga-blockchain while remaining safely on the main-blockchain. The transactions that succeed can then be used to acquire more main-blockchain coins upon which the cycle repeats. Eventually the blockchain with the most financial resources behind it will continue to grow at a faster pace, while the other slowly, and eventually stops growing altogether.

Those siding with the wrong chain who end up accepting duplicated transactions from the other chain, such as a purchase from an exchange running on the losing blockchain, will lose those coins when the dust settles. No war is without casulties, the Great Blockchain Civil War will be no different.

Edit: The first instance described in the article was a soft fork and not a hard fork. The 2nd instance is in debate of whether or not it was non-deterministic behavior or a true hard fork.