The causal chain from the assassination of Archduke Ferdinand to the invasion of Belgium by Germany is far too long and convoluted to argue that it was "inevitable" that war was going to happen. However, a short summary of the chain is worth examining:

1. Ferdinand assassinated in Sarajevo on 28 June 1914
2. Hardliners within the Austrian government advocate for an adversarial stance towards Serbia
3. Germany agrees to unconditional support for Austria-Hungary on July 6
4. Emboldened, Austria issues an ultimatum to Serbia who accept almost all provisions but decline a key one surrounding who would be able to investigate and try the assassins
5. Austria breaks off diplomatic communications, Serbia mobilises its army on July 25
6. Russia, as a Serbian ally, begins mobilisation as well
7. On July 31, Germany demands that Russia halt its mobilisation
8. Following Russian refusal, Germany begins mobilisation. However, due to the nature of the Schlieffen Plan, German mobilisation was largely directed towards France
9. Over the next few days, Germany declares war on Russia, France declines to remain neutral in the conflict, Germany declares war on France and Germany threatens Belgium with violation of her neutrality unless she allows free passage of German troops
10. German passage across Belgium triggers the Treaty of London and causes Britain to declare war

Taken like that, it all seems inevitable... a pre-ordained march towards war that could not possibly be stopped. But now, more than a century after the July Crisis, historians still have not reached a verdict on the question of whether or not war was unavoidable.

That Germany wanted war is an almost incontrovertible position. They felt hemmed in on all sides by the Triple Entente and were feeling economically disadvantaged by their lack of overseas colonies. The Schlieffen Plan was also an outgrowth of the stunning success of the Franco-Prussian war of 1870 and the feeling that they could quickly knock France out of any war.

That France wanted war is less clear but they definitely recognised the danger of Germany and were very keen to ally themselves with Russia to present a threat to Germany on both sides should war break out. Ironically, this fuelled German fears about the constriction of their territory.

Britain almost certainly did not wish for war and was acting more to protect her vast Empire and trading networks. The naval race with Germany was all but over prior to the outbreak of war and there were signs from the Home Office that the British were displeased with Russian interference in Persia and India and that overtures to Germany may prove useful.

Austria also did not want a massive European war but were pushing their historical control over Serbia again. Due to the fallout from the Balkan Wars of 1912-13, the politics of this region were incredibly complex and fraught with tension.

Russia was flexing its muscles and this alarmed Germany. The leading opinion was that war would have to be fought with Russia in "the next few years" lest Russia become too large and modernised to handle.

But was it all inevitable? I contend that the answer is yes but you'll find many voices which say otherwise. Austria, as a declining power, could have accepted Serbian calls for independence. Russia could have interfered less belligerently in the Balkans. Germany did not have to give carte blance to Austria in terms of diplomatic support.

In the end though, we'll never really know.

• Clark, Christopher (2013). The Sleepwalkers: How Europe Went to War in 1914
• Tuchman, Barbara (1962). The Guns of August

I agree it's a complex question and you can go both ways with it.

I would say it was definitely avoidable in that the war resulted from actively chosen decisions made by the leadership of multiple countries. Any number of choices, if made differently, would have prevented this war. If Pasic acts with energy and purpose and stops the assassination (by providing the Austrian government a real warning). If Germany doesn't back Austria. If Russia doesn't back Serbia. If France doesn't back Russia. Each of those items was a decision accepted and made, and each one in that chain was more and more clearly linked with general European war. France choosing to back Russia and encourage them to escalate was much more certain to lead to general war than Germany agreeing to support Austria in punitive action against Serbia. Perhaps, even, if Britain had been more clear on it's intentions it would have changed the outcome (but, perhaps not). Although Christopher Clark goes perhaps too far in overlooking German actions to make his point, Clark does a thorough job of illustrating this precise point in Sleepwalkers.

On the other hand, each party made the decisions it made due to their current evaluation of various strategic goals on situations. German, Austria, Russia, and France all had reasons to fear that the strategic situation "later" would be worse that it was at that moment unless they took action to improve their position at that time. Germany feared both Russia and France would be significantly stronger in the coming years due to improvements in armaments and military infrastructure on the Russian side (both generally financed by France) and larger active and reserve manpower pools on the French side (the new 3 year service law). Germany also feared that failing to support Austria in what they did sincerely hope would be a local Austro-Serbian conflict would damage their alliance and leave them more isolate than before. Russia feared that failing to back Serbia (who they were not allied to) would leave them without a proxy/client in the Balkans, since they had just "betrayed" their previous favored state Bulgaria during the Balkan Wars in favor of the new one Serbia. Losing both as clients, or losing Bulgaria and seeing Serbia crippled, would clearly set back Russia's strategic goal of either directly or indirectly controlling the Turkish Straits. France worried that failing to back Russia AGAIN (after not being interested in a Balkan provocation in 1907/08 and 1912/13) might irreparably damage their alliance with Russia and either lead Russia to find a new path forward diplomatically or to be less than supportive when France was in need (as they were in the 1905 and 1911 Moroccan crises). Austria had legitimate grievances against Serbian actions and felt that if they simply let this incident slide it would lead to increasing provocations in addition to the loss of prestige. Clark also covers these topics in Sleepwalkers, but you can find discussions of the subjects in Strachans The First World War: To Arms (which is admittedly very dense and wide ranging) and Holger Herwig's The First World War: Germany and Austria-Hungary.

The evaluation of these strategic situations would have changed very slowly, if at all, meaning that the conditions for a general conflict would have remained in place for some time, so perhaps the conflict was inevitable from the stance of "if it wasn't this trigger, it would have just been a different one."

In general, I don't like the "inevitable" line of thought as it tends to be used to excuse (either explicitly or implicitly) the actions of the leaders in all the relevant nations. War didn't just HAPPEN to France, French leadership clearly and demonstrably played a role in creating that war and could have prevented it. Same goes for Germany, Austria, Serbia, Russia, and Britain. Only the Belgians and Luxembourgers can honestly claim that war was forced onto them.

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In the “ottoman endgame” (will cite author later) there is an argument that ww1 was inevitable but that the assassination was just the first in a set of potential flashpoints in the balkans that would lead to war.

Iirc the author specifically suggests that Greece would have invaded turkey within the next six months if ww1 didn’t break out. I can’t recall exactly why the author thought this would bring about ww1. If someone is familiar they can fill in the blanks.

Edit - author is Sean mcmeekin

My understanding is that the unconditional support for Austria by Germany was closer to trying to prevent a war rather than causing one. Sort of like how you don't declare nuclear war on a country with nuclear bombs. When Serbia capitulated on almost all the demands Germany thought the war was effectively prevented. Austria seems to have been the one who really wanted war.