system
Given the following post, respond as if you're commenting on Reddit:
human
[Culture] What caused the Culture's shift in mentality between the Idiran War and encounter with the Empire of Azad?

I've just begun the Culture Series, and I'm curious why the Culture seems to have such different attitude towards alien civilizations in the 700 years between *Consider Phlebas* and *Player of Games*.  According to the text the Culture tolerated the Idiran's militant aggression for centuries before finally committing to war.  They were described as being slow to rouse, sort of live and let live, unless pushed too far.

But then they discover the Empire and almost immediately enact a plan to destroy it.  At the end, the drone Flere-Imsaho basically says that the Empire was doom to fall anyway, but they really wanted to hasten its demise.  So pretty shortly after first contact (<100 years?), the Culture caused the complete collapse of that civilization.

Why such a difference?  The Empire was perhaps more brutal and dystopian  as a society, compared to the Idirans.  But the Idirans were very much opposed to the Culture's philosophy of life, and they posed a much greater threat.

Alternative theory: Special Circumstances was deeply involved in starting a war in both cases, but they just had a easier time with the Empire?
gpt
Despite its appearance to outsiders as a united blob of action, the Culture is *extremely* fractured internally, and it has almost no checks or balances on what individual actors are able to do.

The Idiran Empire was shockingly close to the Culture in terms of technological level, and they had backing from at least one other equiv-tech civilization which wanted to check the Culture's influence.  Any individual Culture ship, or small group, would have simply been destroyed if it had decided to unilaterally go to war with the Idirans.  The war needed the support of a large majority of Culture individuals, and getting majority support on *anything* in the Culture is like herding cats.

Azad, by comparison, was tiny.  Their technology was so far behind the Culture that it was essentially impossible for an Azadian to detect clandestine operations from the Culture.  A single culture ship could have successfully invaded the entire empire, and destroyed it by force if it decided this was a necessary course of action.

Since unanimous agreement was not necessary, no time was wasted in seeking it.  A small group (maybe even just an individual mind) in Special Circumstances decided on the course of action, and no other minds objected strongly enough to oppose them.