During World War I, both breweries, along with all other industries, experienced a major crisis. Due to the draft, the breweries Staropramen and Ostravar lost their most skilled workers. Raw materials and machinery was seized to aid the war effort.
Staropramen Brewery, for example, limited production and brewed four- or at most six-degree beer. When the War ended and the new Republic was formed, the situation did not change – raw materials were still in short supply, many of the best workers did not return from the front, and beer was brewed from substitute ingredients. The situation was the same at Ostravar, where annual production during World War I fell to a mere 3,700 hecto-litres and "war beer" had only five degrees.