Did France & Italy continue to develop and manufacture sophisticated military hardware once under German control?

Question

Both France and Italy were designing and building advanced vehicle engines, motorcyles, aero engines and airframes through the 1930s and early 1940s.

In the case of those advanced economies of Europe (principally France and Italy, but also Czechoslovakia and the Netherlands) which fell under German control (direct or otherwise) between 1940 and 1945, what happened to their production of advanced military hardware like tanks, aero engines, airframes and the like?

Sure, plant and personnel were harnessed to the German war effort but what were they making? Were their own designs dumped, and the factories turned over to German designs to order? Or were they downgraded to producing more basic items like shells and pots and pans? Or were they permitted/encouraged to carry on independently producing their existing designs and even develop new prototypes? If the latter, were there German units in 1944/5 driving/riding/flying Renault trucks and Fiat aircraft?

Answer 1

Italy was an ally of Germany, not an occupied country (except for the North in 1943-1945, which was not, technically, occupied). They made, e.g., Fiat_G.55 in Turin which saw action against the allied air forces.

In general, Germany had the full use of the whole of French, Czech &c industries (except for those which were destroyed by allied bombing and/or local sabotage, which was not much), although some individual designers escaped (some with designs).

Specifically:

Renault:

After the French capitulation in 1940, Louis Renault refused to produce tanks for Nazi Germany, which took control of his factories. He produced lorries for the German occupiers instead. On 3 March 1942, the RAF launched ... bombers at the Billancourt plant... Renault resolved to rebuild the factory as quickly as possible, but a further heavy bombardment ...

Citroën:

During the German occupation of France in World War II Boulanger refused to meet Dr. Ferdinand Porsche or communicate with the German authorities except through intermediaries. He organised a "go slow" on production of trucks for the Wehrmacht, many of which were sabotaged at the factory, by putting the notch on the oil dipstick in the wrong place, resulting in engine seizure.

Tatra:

After the 1938 invasion of Czechoslovakia by Nazi Germany, Tatras continued in production, largely because Germans liked the cars

Avions Amiot:

During the war, Amiot co-operated with the German occupiers to protect his interests, .... Amiot became a subcontractor for the Junkers company, building 370 aircraft.