Describe the motivation behind Britain and France's ultimate declaration of war on Germany?

The motivation is that Britian and France got angry when they found out that Germany invaded Belgium which was the first ever battle and start of the First World War (Battle of Liege). Germany invaded Belgium because they wanted to invade France inspired by The Schlieffen Plan which means they charge at France at lightning speed while Russia gets ready for war since they're so big and clumpy and then also charge Russia at lightning speed. But that plan failed since Belgium was strong enough to hold to Germans back. Austria - Hungary got angry at Serbia since they might have assasinated Ferdinand so they declare war on each other. Germany attacks the other countries fearing they might get involved too since France, Russia, and Britian are allies with Serbia.

Explanation:

in 476 c.e. romulus, the last of the roman emperors in the west, was overthrown by the germanic leader odoacer, who became the first barbarian to rule in rome. the order that the roman empire had brought to western europe for 1000 years was no more.

it's lower nubia : ) good luck