This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.

During the First World War, Plymouth was the port of entry for many troops from around the Empire and also developed as a facility for the manufacture of munitions. Although major units of the Royal Navy moved to the safety of Scapa Flow, Devonport was an important base for escort vessels and repairs. Flying boats operated from Mount Batten.
What was the primary base of the Royal navy during World War I?