Modern Britain in 1939 would win early but face a supply clock

What if present-day Britain and its armed forces were sent back to spring 1939?

Modern aircraft and armor would dominate early fighting, but ammunition and support for systems that 1939 industry could not replace would become the limiting factors.

Modern British aircraft, precision-guided weapons, and armored vehicles would badly outclass 1939 opponents. Existing refineries and industrial infrastructure would help the force operate, while Prince of Wales could be adapted to aircraft available in the period. The advantage would still depend on ammunition, spare parts, and the ability to reproduce modern systems. The closing question about tanks running out of rounds before targets captures the main limit: tactical dominance does not remove the supply clock.