Charles de Gaulle had a military background, but he quickly became the political figurehead of the Free French Movement that was based in Great Britain during World War Two.
Vocabulary is generally an uncountable, or mass noun in English. It's neither singular or plural, however it is treated as singular for the purposes of verb conjugation, as most uncountable/mass nouns are. You can use the word “vocabularies” but only when you are talking about different kinds/sets of vocabulary."
There would be more context to be added to this answer.
Thanks much,
ROR
