Which nation would most likely have the biggest advantage during a European war, and why? Great Britain, because they had the most warships to complement their small army. Germany, because most of the fighting would be on land and they had the largest army. France, because if they called up their reservists their army would be larger than Germany's. France, because of the combined numbers of their army, reservists, and warships.

Actually it will always depend on the commanders and type of battle that will commences. Also it will depend on the economic stature of the country and whether it could outwit the other countries in case of war of attrition. Each of the country has their own strength and weaknesses that can attribute to the victory and defeat of the country. If we would based the performance between the three countries in world war 2 period, Germany can oust the two countries in a fast war based on the army size. If it would be a naval combat based on the choices it would be Great Britain can win due to the advantage but statistics can only forecast and can't be an accurate based on victory like the U-boat campaign of the Germans that damage the prestige of the Royal Navy. If in reserves and manpower the French could muster a large amount of men and has an average size of army and navy that can stand a battle against the other countries stated.