Which country was the last to declare war after several unsuccessful attempts at peace in 1914?

Enormous fatalities had been caused on France and two fifths of France’s military casualties were incurred in 1914. The troops of Germany engaged a large area of northern France including an important proportion of French industrial capacity and mineral wealth. It was dominated the second phase of the war in the west. This took from November 1914 until march 1918. It was considered by the unsuccessful attempts of the French and their British allies to evict the German armies from French and Belgian area.