WWI (1914-1918) was a disastrous conflict between two sides - the Allied Powers and the Central Powers. It resulted in the victory of the Allies. There were plenty of Central Powers weaknesses, the Schlieffen plan, weak allies of Germany and their hard economic situation at the end of the WWI. However, it was not only due to these weaknesses, Allied Powers had a few strengths, that made them won. The most important of these are : greater army, control of the sea and support of the USA since 1917, while Germany was already running out of supplies and soldiers.

One of the earliest causes of the Allied Powers victory was the failure of the German Schlieffen Plan. Its aim was to occupy the France, coming through the Belgium, and then, when these would be under their control, it would create one big front to fight with Russia. Unfortunately, everything went wrong, Belgium soldiers were extremely brave, what delayed the German advance. Germany did not manage to break through to France as quickly as it intented to. Due to the "Treaty of London", which guaranteed the independence of Belgium, Britain declared war on Germany. 125000 of well trained and equipped members of BEF (British Expeditionary Force) helped to resist the assault. A crucial element of failure of the Schlieffen Plan was the fact, that Russia organised it 's army earlier than Germany suspected, what forced it to send soldiers away to Western Front and fight off the Russian troops invasion.
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