His nickname "the Terrible" was a result of his harsh treatment of the Boyars, the Moldavian nobility, which at that time were very influential in deciding the rulers of the small principality.

Attempting to strengthen his rule and make an example out of disloyal nobles, Ioan III carried out several Boyar executions, thus earning his alias "the Terrible".

The common people appreciated his courageous stand against the nobility's corruption and the harsh Turkish domination.

He refused to double the amount of tribute paid to the Ottomans but the Moldovan army was defeated in the Battle of Cahul Lake, he was captured and executed.

[2] His short reign was marked by fierce combat against the Ottoman Empire and their Crimean Tatar allies.