So the legal female heir to the throne, Duchess Anna Maria Franziska, and her sister Sibylle of Saxe-Lauenburg fought for the succession of the former, the elder of them.

Their weakness was abused by Duke George William of the neighbouring Brunswick-Lunenburgian Principality of Lunenburg-Celle, who invaded Saxe-Lauenburg with his troops, thus inhibiting Anna Maria's ascension as Duchess regnant.

Also other monarchies claimed the succession, evoking a conflict further involving the neighbouring duchies of Mecklenburg-Schwerin and of Danish Holstein, as well as the five Ascanian-ruled Principalities of Anhalt, the Electorate of Saxony, which had succeeded the Saxe-Wittenbergian Ascanians in 1422, Sweden and Brandenburg.

Only in 1728 his son Emperor Charles VI enfeoffed George II of Great Britain with Saxe-Lauenburg, finally legitimising the de facto takeover by his grandfather in 1689 and 1693.

Cosimo III de' Medici coaxed his son into marrying Anna Maria Franziska for dynastic purposes, she was very wealthy, and brought a possible claim to the Duchy of Saxe-Lauenburg through her father.

They were married on 2 July 1697 by the Bishop of Osnabruck at Düsseldorf but they lived in the Kingdom of Bohemia, at chateaux of Ploskovice (Ploschkowitz) and Zákupy (Reichstadt).

He asked the Pope, Clement XI, to send the Archbishop of Prague to reproach her, and convince her to fulfil her wifely obligations.

As Grand Duchess, Anna Maria Franziska kept to her life of solitude at her castle, where she talked to the horses in the stables.

As the Medici had no male heir, Francis Stephen of Lorraine (later Holy Roman Emperor) ascended the grand ducal throne.