The were multiple, overlapping and sometimes contradictory imperatives at work when Napoleon created the Illyrian Provinces in 1809. The main rationale for Napoleon was that the Illyrian Provinces would strengthen the Continental System by putting a large swath of the Adriatic under direct French control. This would strengthen the blockade and end smuggling. Napoleon operated under the general logic that Austria had proven susceptible to British influence and that by eliminating her outlet to the sea, France could gain a more pliant ally on the continent. The French strategic rationale was also that they could create a buffer state in the Balkans on the flank of Southeastern Europe which would act analogous to the Duchy of Warsaw. They would be a direct source for manpower and revenue for French interests in this region of Europe. The erection of the Illyrian Provinces was also of a piece with Napoleon's various annexations of other territories like Holland and the Papal States. Unlike other voices within the French government, Napoleon conceived of citizenship as jus sli (from the soil) in which Frenchmen could be made through acculturation to French norms and values. So the Illyrian Provinces fit within Napoleon's conception of the universal French empire he was creating.

That said, the Illyrian Provinces never played the role Napoleon intended for them. They were never legally incorporated into the French state via a Senatorial resolution, and thus were in a legal state of limbo. Most of Napoleon's government conceived of citizenship on the basis of jus sanguine (by blood) which precluded any attempt to create a sort of universalized French citizenship. Napoleon himself was reluctant to get France too involved in the Balkans; French reforms were half-hearted and even those yielded meager results. The French Emperor would keep prospect of returning the provinces to Austria as a potential inducement to keep Austria on France's side in 1812. The weakness of Marmont's administration meant that smuggling flourished and thus its role as an Adriatic cordon against Britain failed. The blockade further ruined the Adriatic economy and added economic hardship to the region, so the French interlude was seldom eulogized by subsequent nationalists on the scale of the Duchy of Warsaw. The Illyrian Provinces thus became a footnote for the larger failures of Napoleon's empire.

Sources

Broers, Michael. Europe Under Napoleon 1799-1815. London: Arnold, 1996.

Broers, Michael, Peter Hicks, and Agustín Guimerá Ravina. The Napoleonic Empire and the New European Political Culture. Basingstoke, Hampshire : Palgrave Macmillan, 2012.

Dwyer, Philip G. Napoleon and Europe. Harlow, England: Longman, 2001.

Grab, Alexander I. Napoleon and the Transformation of Europe. New York: Palgrave Macmillan, 2003.