In 1914 Germany issued a warning declaring that the waters around Britain and Ireland were a war zone. Do you believe that Germany had any justification for resorting to unrestricted submarine warfare in World War I?

Germany didn't had any justification for such actions.

Explanation:

At the beginning of the 20th century Germany was a growing power. While the country had everything needed in order to progress economically and strengthen it positions it turned to use other methods. Germany was already granted some colonies so it had places from where to extract free resources. The country itself is rich in natural resources and it also had large and young labor force.

Instead of using these advantages to progress as a country Germany took up a policy of expansionism, or rather trying to destroy the other powerhouses in Europe. This resulted in Germany declaring international waters as war zone, as well as staring to have military intervention across the continent which resulted in the World War I. The end result for Germany was terrible, as from country that was on the rise it found itself destroyed and in terrible conditions.