When I see maps of the first French empire at it's territorial peak, there is often a great distinction between France and it's added territory - which are often showcased in dark blue - against the client states, often shown in light blue.
That's why I was shocked to see territory in the balkans being dark blue. Can anybody shed some light on this?
Napoleon took several of the border provinces (of the Grenz or military frontier) as part of the territorial settlement following his victory during the War of the 5th Coalition - these are usually known as the Illyrian Provinces. The primary driver was to cut off access to trade through the Adriatic to enforce the continental blockade. The region existed in a legal limbo and was not really ruled from Paris, but rather by the local French governors who mostly left things as they were - the local military forces, for example, were just the Austrian border regiments given a new title.
u/kieslowskifan goes into more detail here