The hot months of summer are always ripe for war. As battles continue today in Gaza, Syria, and Iraq and tensions remain high in Ukraine, international events during the “July Crisis” were just as hot, if not more so, 100 years ago.

On 28 June 1914, Serbian nationalists assassinated the heir to the Austro-Hungarian throne, Archduke Franz Ferdinand in Sarajevo. Franz Joseph, Kaiser of Austria-Hungary, interpreted the killing as a direct provocation by the Serbian national government, though there was no clear evidence of their collusion. He issued a list of demands—the “July Ultimatum”—to the Serbian government, the trick being that he expected them to fail to answer them. At the same time, Austria-Hungary’s close ally, Germany, and Kaiser Wilhelm II gave Kaiser Franz Joseph a “Blank Check” that Berlin would support Vienna in any war—despite the fact that Russia, allied with France and Britain, had sworn to protect Serbia from any Austro-Hungarian aggression. The trap was set and WWI was almost destined to begin.

Surprisingly, Serbia met virtually all of Austria-Hungary’s demands by 28 July and appears to have genuinely wanted to avoid the trap set for them by Vienna. Here was an opportunity for things to have turned out very differently. After receiving a copy of the Serbian answer, Kaiser Wilhelm II saw little need for the German states to go to war in Serbia since Vienna had obtained virtually all of the concessions it had demanded. He wrote that he would not have promised Berlin’s support to Franz Joseph had he known it would be on such basis. Nonetheless, Vienna declared war on Serbia the same day and Germany remained loyal to its pledge to support Austria-Hungary.

The lamps are going out all over Europe. We shall not see them lit again during our lifetime.

Following the Austro-Hungarian declaration of war against Serbia, Russia mobilized its own troops for the defense of Serbia. In reaction to Russia’s mobilization, Germany mobilized its own Army and declared war against Russia on 1 August 1914. Russia had allied itself by treaty with France and, as a result, Germany declared war on France on 3 August 1914. This declaration set into motion the German military staff’s “von Schlieffen Plan”.

Stalemate in the trenches of Europe eventually pulled the reluctant giant America into the war. It also pulled in colonial troops from all corners of the world and ignited proxy wars and triggered defense pacts in Africa, the Middle East, and Asia. One ultimatum doomed to fail and one unconsidered promise dragged virtually the entire world into war, aggravated by a network of colonial concerns and defense treaties.Knowing that France had built up great defenses along its border with Germany, the von Schlieffen Plan called for German troops to avoid them by first invading neutral and undefended Belgium and Luxembourg and attacking through them into north-eastern France. This attack and its own alliance with France pulled Great Britain into a coalition with France and Russia. Five of the world’s mightiest nations were at war.

As the July Crisis unfolded and World War I began, British Foreign Secretary Sir Edward Grey remarked, The lamps are going out all over Europe. We shall not see them lit again during our lifetime. What lessons can be drawn from the Great War to be applied to the world today?

• Be careful what you promise your friends and understand exactly what your friends have promised you. Most major Western states have pledged to defend Israel and recognize its right to exist and to defend itself. Rightly so. However, they have not written a “Blank Check” to Israel to conduct its wars or defensive actions in any manner it sees fit or to support all of its actions in any and all circumstances. Western presidents and prime ministers are not Kaiser Wilhelm II and Israel would do well to recognize this. So would those Western presidents and prime ministers. Israel should strongly consider whether victory in Gaza is worth risking the loss of a lot of friends. Western states should also consider at what point the cost of supporting Israel becomes too high.

• Seemingly small events can have grave international consequences: The killing of one man by an independent group of nationalists triggered state actions that pulled all of the world’s developed nations into a world war. None of the parties considered the web of consequences such an event would have. Some were unforeseeable. Vladimir Putin appears to be gauging just how far Russia can push its chips forward before it elicits a serious response from the West. So far, the West has exhibited quite a high tolerance for pain and a will for peace, even at high cost. It has been largely thwarted by Russian maneuvering and information warfare in Syria, stood by as Moscow annexed Crimea under the thinnest of pretenses, and has so far acted with great restraint after Russian-controlled separatists downed a civilian airliner half-filled with European citizens. In other circumstances, the pro-Russian rebels and their BUK anti-aircraft missile could have played the role of the Serbian nationalist who killed Franz Ferdinand. It has not turned out that way. However, if Vladimir Putin continues to probe the West’s pain threshold, it still could. Moscow may have tested usually-forgiving European nerves—especially in the Netherlands—to the breaking point. Which states would line up on the Western side is generally clear. But who would line up in support alongside Vladimir Putin? This is something Putin himself should consider just as much as the West. Russia should also weigh up after this event whether undisciplined, trigger-happy rebels could push Moscow’s chips further forward than they want to.

• The war you want may not be the war you get: The 9/11 attacks were the assassination of Franz Ferdinand. Much like the “July Ultimatum” of 1914 from Austria-Hungary to Serbia, in 2002 the U.S. issued Saddam Hussein, who had nothing to do with 9/11, a doomed-to-fail ultimatum to declare WMD stockpiles he did not have. The United States wanted one war in Iraq—a war of liberation from evil and tyranny—and got another—a grinding counterinsurgency and a nation to rebuild—which continues to have great and terrible consequences years down the road. Tony Blair played Kaiser Wilhelm II. Though the Global War on Terror was not WWIII, it has pulled America, Britain and its allies into a worldwide fight against terrorism and extremism in their own major cities and counterinsurgency battles across Africa, the Middle East, and Asia which continue today. Much like many of the soldiers of WWI on all sides who eventually returned home from the trenches, many of the veterans of the Global War on Terror are left scratching their heads as to what any of it has actually achieved. Even more so following ISIS’s invasion and occupation of western Iraq. And much like their WWI veteran forebears, today’s veterans are not being very well served in return by their country, as the current crisis in Congress and at the Department of Veterans Affairs shows.

Chris Miller is a U.S. Army veteran and Purple Heart recipient following two tours in Baghdad, Iraq and has worked as a military contractor in the Middle East. His work currently focuses on strategic studies. His interests are CBRN, military and veterans issues, the Cold War, and international security affairs.

[Photos: Flickr Commons: 1) Royal Opera House Covent Garden 2) Europeana Newspapers]