In the late 1930s, there were only three existing slipways capable of building large ships: The No. 4 dock at Brest and the "Forme Caquot" and No. 1 docks in Saint-Nazaire. The No. 4 dock was only , too short to build any vessel larger than the "Richelieu"s (which themselves had to be built without their bow or stern and completed after launching), and the No. 1 dock in Saint-Nazaire was already occupied with building the aircraft carrier (and was slated to begin construction of her sister after the latter's projected launch in 1941).