 Complete the following phrase:  At the beginning of the war, Germany had the most advanced chemical industry in the world, accounting for more than 80 of the worlds dye and chemical production. Although the use of poison gas had been banned by the Hague Conventions of 1899 and 1907, Germany turned to this industry for what it hoped would be a decisive weapon to break the deadlock of trench warfare. Chlorine gas was first used on the battlefield in April 1915 at the 