What Would have happened if serbia completely accepted the ultimatum?
World War I was completely unnecessary and actually should not have become a world war. The assassination of Archduke Franz Ferdinand of the Austria-Hungarian Empire occurred in Sarajevo, Bosnia and Herzegovina. We all know that Serbia was blamed by Austria-Hungary, and that Serbia was given an ultimatum by the empire to accept in under 48 hours. Serbia agreed with every part of the ultimatum but one: for Austria-Hungarian officials to enter and investigate Serbia for proof of their link of the assassination. Though Serbia had nothing to hide and were well aware that they had no involvement with the assassination, one crucial aspect appeared within the people: nationalism (the intense loyalty to a group or country). Nationalism was and is still widely known throughout the Balkan region. With nationalism, Serbia were out to prove that they were a strong, tough, and independent country that did not need the help of the empire above to investigate their country.
See, if Serbia had not been overthrown by the power of their nationalism and simply accepted the ultimatum, the problem would have been easily solved and no conflict would appear between the two countries that should have only been involved. But, since Serbia rejected the ultimatum, Austria-Hungary had declared war on Serbia and sent troops to their border. This was supposed to be a battle only between the two countries. But what could have possibly caused this to become a world war situation? There are many reasons to this, but one can be very obvious: alliances.
What if Russia has stayed out of the conflict?
With the powerful countries of Europe forming alliances to protect each other and balance peace, this kept the nations even between each other. The Triple Entente consisted of Great Britain, France, Russia, and later, Italy. The other alliance, the Central Powers or the Triple Alliance, had only consisted of Germany, Austria-Hungary, and the Ottoman Empire. But, how had Russia involved themselves with the opposing alliance and a small country that had no part with either of them? Prior to this, Balkans and Slavs had been attempting to gain independence from the Austria-Hungarian Empire. Slavs were around the border of Russia, which was a large country filled with Slavs. Balkans and Slavs were nationalistic and often thought as somehow related between each other because of similarity in language and many other reasons. Russia, though, protected Serbia for this reason. Instead of allowing this battle to be between only countries that had a problem with an ultimatum, Russia decided to intervene and send their troops to Serbia to help. Although Serbia had an advantage, this caused the nations of other alliances to be pulled into the conflict: "If Russia had joined the war, then our country of Germany should participate to even out and help Austria-Hungary!". This thought continued and spread, and as more and more nations began to be involved, it eventually resulted in a world war. America decides to later join to protect Great Britain after a British ocean liner called the "Lusitania" had been sunk by German U-boats.
What If...Germany won WWI?
World War II resulted in Germany's loss and humiliation of WWI. The country was humiliated and blamed for every single aspect of the war. They were forced to pay reparations for damage, disarm their army completely, give up territory and over-sea colonies, etc. Although Germany was maybe one of the last reasons that the war actually started, they were blamed. The Treaty of Versailles that ended WWI contained all of these demands from the other nations. Germans felt their government has betrayed them, so many turned to radical parties, such as Hitler's German Workers' Party (GWP), that disagreed with the treaty and planned their own government. So many Germans supported radical parties that Hitler was able to be named Chancellor of Germany by President von Hindenburg. When von Hindenburg passed away, Hitler was able to unite the two positions to gain all control of power, hence starting another world war and killing millions of Jews.
So, if Germany had not been blamed for starting WWI and had actually won, would any of WWII actually have happened? If the Treaty of Versailles had not blamed Germany, would another world war occur? Would Hitler have risen in power at all? The answer seems like this most likely would not have occurred: Germans, such as Hitler, would not have been angry at their government, resulting in no reason for radical parties to even exist. No radical parties mean no rise of anti-Semitism, and therefore, no WWII.
How would the world be like today without the world wars?
The world would be much different, in my opinion. We would not have to learn about Adolf Hitler and his discrimination of Jews, millions would not have died...we would all be happier. No divisions between religions and nationalities. The Great Depression would probably not have occurred, too. The First World War could have been avoided, leading to a second world war that probably would not even occur.
If Serbia accepted the ultimatum, a battle would only occur between the two nations. If Russia had not participated, therefore influencing other countries to do also, the war would not have become a world war. If Germany had won WWI, a second world war would not have happened. The world would have been better. These reasons, and many others, lead to the causes of a world war that should never have been.