Austria-Hungary and Germany saw an opportunity to conquer and took it

The argument

The assassination of Archduke Franz Ferdinand should not be written off as an unfortunate incident with disproportionate consequences inciting an entire world war. It was clear that the drift growing between European powers led the duo of Austria-Hungary and Germany to go on the offensive, using the assassination as a guise. The balance of power in the European theater was veering away from Austria and Germany, resulting in them entering a state of policy where they would need to restate their own dominance in an effort of self-preservation. Specifically, the Austrians were already threatened by Serbian ambition in the Balkans and had felt a need to secure themselves in that sphere. The assassination resulted in an increased threat of military invasion, backing Austria and Germany further into their corner of the continent.

Premises

Counter-arguments

Austria-Hungary was Germany's only ally. They flanked Austria-Hungary with a goal of self-preservation, considering the rest of the actors in the theater viewed them as a threat to be removed. Due to this necessity for self-preservation, Austria and Germany should not be viewed as the instigators of the conflict since they were acting purely in response to tensions formed by other powers.

Rejecting the premises

[Rejecting P1] Treating the assassination as a "guise" attributes a prior intention to conquer that the premise does not evidence; a state reacting opportunistically to a crisis it did not create is differently placed from one that engineered a pretext, and the argument treats the two as equivalent. [Rejecting P2] A shifting balance of power and Serbian ambition in the Balkans are the counter's own material for describing both powers as acting defensively, so the same facts underdetermine whether "conquest" or "self-preservation" is the right description — and the other powers whose pressure produced that drift go unexamined.