Overall, Louis's diplomacy and warfare with the Slavs in the decade after Verdun demonstrate his determination to reestablish the traditional Carolingian tributary lordship over the Slavs as well as the considerable obstacles to this policy.

Taken from Struggle for Empire: Kingship and Conflict Under Louis the German, 817 – 876, by Eric J. Goldberg.

Louis the German is grandson of Charlemagne and ruler of the eastern kingdom (and sometimes more, depending on his relative power and standing with his father, Louis the Pious).  To his east are the troublesome Slavs.

Apropos to this time of Brexit and consistent with my views of decentralization as against the desires of those who wish to control and exploit man (if nothing else, proving that I am quite capable of finding and focusing on only tidbits of information that support my previously established views…), I offer the following punchline to this desire of the aforementioned Louis:

By the ninth century, however, Slavic rulers posed serious challenges to the Franks. Because the Slavs were divided among numerous princes and lords, Louis was forced to carry out diplomacy with scores of individual Slavic rulers.

"Take me to your leader" works easily in the consolidated Europe; not so easily if one must overcome 20 or 30 different leaders, or better yet 200 or 300.  It was true 1200 years ago; it is true today.