Arnulf, according to the Annals of Fulda, had sent an embassy led by margrave Arbo to Moravia sometime during 891 in order to renew the peace between Moravia and Eastern Francia.
A letter written by the margrave had soon announced that the legates were returning from Svatopluk and the Moravians who had agreed "to give themselves in friendship".
Svatopluk, however, had broken his pledges; thus, Arnulf decided to invade Moravia in 891.
First the king met with Braslav, the Slavic dux on the river Sava, next raised an army of Franconians, Bavarians and Alamanni, and also recruited Hungarians to join his campaign.
Because of his desire to bring down Moravia, Arnulf will be accused by Ottonian authors in the late tenth century of unleashing the Hungarians on Europe.
Arnulf's invasion of Moravia had started in July 892, but he had failed to defeat Svatopluk, who has brought the Moravian kingdom to its greatest height.
The war against Moravia seems to have continued until 894, the year of Svatopluk's "most unlucky death" according to the Annals of Fulda, which implies that he met his end in some kind of mishap, the sort that occurs in war.
The exact circumstances of Svatopluk's death, however, are unknown.
Zwentibald, the dux of the Moravians and the source of all treachery, who had disturbed all the lands around him with tricks and cunning and circled around thirsting for human blood, made an unhappy end, exhorting his men at the last that they should not be lovers of peace but rather continue in enmity with their neighbors.-- Annals of Fulda (year 894).
Arnulf ends Moravian assaults by treaty in 894.
