And lastly Britain declared war on Germany when they invaded Belgium to attack France. It is clear that the alliance system that was in place in Europe at that time was the key reason why the war that started on the 28th of July 1914 became a World War. Each alliance included different countries, in Germany's case they were fighting along side with Austro-Hungary and Italy, which joined later on and therefore we cannot only blame Germany for causing the outbreak of the First World War but if we are to blame anybody we must blame the whole alliance in such case, hence Germany was definitely involved, nevertheless they cannot be blamed to the full extent. .
Secondly, there is no dispute that the assassination of the archduke Franz Ferdinand was the trigger of the First World War. The archduke was the heir to the throne of Austria. The organization that had him assassinated was a Serbian nationalist group. Austria demanded the right to investigate inside Serbia and the freedom to deal with the members of the group as they pleased, which would have had been an extreme violation of Serbian sovereignty and was demanded with the expectation that it would be refused. Serbia refused, and Austria mobilized its military against them. Russia on the other hand mobilized its military, in defence of Serbia. The mutual declarations of war between Austria and Russia triggered the alliance systems, bringing in Germany, France and United Kingdom. Germany's invasion of France via Belgium was the initial act of the war. In this case it was Germany and Germany alone who acted and made first step. This act was named the Schlieffen Plan. The idea was that Germany would first invade France through Belgium and then attack Russia before it could fully mobilized its troops. However, by invading France through Belgium, Great Britain got involved as they had a treaty stating, that if Belgium was to be invaded as a neutral state, Britain would be obliged to aid them.