The Idirans were already at war, conquering the species they regarded as inferior and subjugating them in a primarily religious empire which was only incidentally a commercial one as well. It was clear to them from the start that their jihad to "calm, integrate and instruct" these other species and bring them under the direct eye of their God had to continue and expand, or be meaningless. A halt or moratorium, while possibly making at least as much sense as continued expansion in military, commercial and administrative terms, would negate such militant hegemonisation as a religious concept. Zeal outranked and outshone pragmatism; as with the Culture, it was the principle which mattered.
The war, long before it was finally declared, was regarded by the Idiran high command as a continuation of the permanent hostilities demanded by theological and disciplinary colonisation, involving a quantitative and qualitative escalation of armed conflict of only a limited degree to cope with the relatively equivalent technological expertise of the Culture.
While the Idirans universally assumed that having made their point the people in the Culture would back down, a few of the Idiran policy-makers anticipated that, should the Culture prove as determined as a "worst possible" scenario projected, a politically judicious settlement might be arrived at which would save face and have advantages for both sides. This would involve a pact or treaty in which the Idirans would effectively agree to slow or limit their expansion for a time, thus allowing the Culture to claim some — but not too much — success, and provide the Idirans with (a) a religiously justifiable excuse for consolidation which would both let the Idiran military machine draw breath and cut the ground from beneath those Idirans who objected to the rate and cruelty of Idiran expansion, and (b) a further reason for an increase in military expenditure, to guarantee that in the next confrontation the Culture, or any other opponent, could be decisively out-armed and destroyed. Only the most fervent and fanatical sections of Idiran society urged or even contemplated a war to the finish, and even so merely counselled continuing the fight against the Culture after and despite the back-down and attempt to sue for peace which they too believed the Culture must inevitably make.
Having drawn up these «no-lose» formulations of the likely course of events, the Idirans joined battle with the Culture without qualm or hesitation.
At worst, they perhaps considered that the war was being begun in an atmosphere of mutual incomprehension. They could not have envisaged that while they were understood almost too perfectly by their enemy, they had comprehensively misapprehended the forces of belief, need — even fear — and morale operating within the Culture.