Complex sentence: The Royal Thai Navy--consisting of several vessels, including two coastal defence ships, twelve torpedo boats and four submarines--was inferior to the French naval forces, but the Royal Thai Air Force held both a quantitative and qualitative edge over l'Armee de l'Air.
Split into simpler sentences: The Royal Thai Navy-consisting of several vessels, including two coastal defence ships, twelve torpedo boats and four submarines-was inferior to the French naval forces. But the Royal Thai Air Force held both a quantitative and qualitative edge over l'Armee de l'Air.