A century ago, every country had its reasons for World War I

Erich Remarque's seminal anti-war novel All Quiet on the Western Front features a moment during battle when the German protagonist shares a shell-hole with a French soldier he stabs and then watches die.

As he goes through the pockets of the dead soldier, examining his papers and photographs of his family, the German realizes that the other soldier was simply a young man like himself and remorsefully whispers, "Forgive me, comrade; how could you be my enemy?"

This scene encapsulates modern attitudes towards the First World War, the conflict that began a century ago and killed 8.5 million combatants. It remains to this day a byword for waste and futility.

Monday, July 28, marks the 100th anniversary of the day that Austria-Hungary declared war on Serbia, starting World War I.

Remarque's book, set during that war, conjures up an image of senseless slaughter, and a slaughter it certainly was. By 1914, defensive military technology — machine guns and light artillery — had outpaced offensive capability, ensuring enormous casualties in battles fought between armies of unprecedented size.

At the same time, the traditional line separating civilians from combatants was slowly being erased, adding to the overall carnage. Many see the First World War, in fact, as merely the bloody precursor to the far deadlier Second World War, which killed over 55 million people.

The tremendous loss of life between 1914 and 1918 quite properly colors everyone's view of the First World War, the gateway to the murderous 20th century. How could destruction on such a vast scale possibly be justified? One of the most compelling myths of the First World War contends that the countries involved entered into it almost by accident, with no real war aims.

This easy dismissal of the reasons for the conflict prevents people from understanding why the war happened and why the countries involved were willing to risk the lives of their citizens to fight it.

In fact, although some of those reasons remain highly controversial, and certainly do not seem defensible a century later, the combatant nations felt they had good reasons to go to war.

Germany desired a position of supremacy in Europe. Austria-Hungary fought for ascendancy in the Balkans and the integrity of its empire. France went to war to defend its territory and combat German militarism. Britain wanted to maintain the balance of power in Europe. Russia had territorial and ethnic interests in the Balkans and sought to prevent German encroachment on its empire.

The United States made a late entry after its neutrality was violated, and then promoted the conflict as an ideological "war for democracy" in Europe. Treaties that promised mutual support drew these nations together, formed the battle lines for the war and transformed the assassination of an Austrian archduke and his wife in the Balkans into a vast global conflict fought on numerous fronts. While there was by no means unanimous support for the war in any of the belligerent nations, citizens on the whole supported their countries' war efforts.

While it is right for us today to look with a skeptical eye on justifications for this or indeed any war, at the same time we need to recognize that in the First World War, millions of people died and sacrificed for causes they found worthwhile.

Wars are not fought in retrospect, as the noted historian Adrian Gregory has observed, and damning the First World War because we find its rationales insufficient 100 years later does a disservice to those who fought in it and gave their lives for what they believed were worthy causes.

Understanding the reasons the countries involved believed they were right to wage the First World War helps honor those who died in it. Analyzing the reasons it was fought helps us to make sense of this supposedly senseless conflict. Acknowledging the sheer destructiveness of the war and understanding the pattern it set for the Second World War should provide the grimmest possible reminder why a third such war ought to remain unthinkable.