He didn't. Britain declared war with Germany.
Germany didn't declare war in 1915 against anyone, it was actually Britain that declared war on Germany
Britain was the first to declare war on Germany and New Zealand and the rest of the commonwealth felt like they wanted to help britain defeat germany
1939
Germany attacked a Poland A British ally.
To response to Germany invasion of Belgium.
Because Germany invaded Poland.
yes
Because of Germany's attack on Poland.
The 1939 invasion of Poland caused Britain to declare war on Germany, which started WWII.
3rd Sept 1939 in europ
France and Britain had promised to declare war if Germany tried to obtain anymore territory. And they kept that promise when Poland was invaded.