The MK9 Corvette was ordered by the Nigerian Navy in April 1975 as follow-ons to the smaller Vosper Thornycroft MK3, which was confusedly grouped under the same Hippo class designation,[1] both ships being named after the word for hippopotamus in local languages.

In 1994-1995 she underwent a refit at Lagos which at least made her seaworthy again, but with some systems off-line.

The Erinomi participated in a December 1995 naval exercise; she rarely left port thereafter until 1997, when minor repairs allowed her to again undertake patrols, but by 2007 the ship was again non-operational.

In 2000 a major repair effort allowed her to leave port again, although with most sensors and some weapons nonfunctional.

In December 2004, the Enyimiri suffered a massive explosion resulting in crew fatalities and severe damage to the ship.