The move by Nigerian President Muhammadu Buhari to sack his military chiefs has come to many as a surprise - given that he had previously ignored calls for their removal.
The outgoing heads had served for about five years - making their tenure the longest since Nigeria returned to democracy in 1999.
They were initially praised for how they dealt the militant group Boko Haram and its splinter faction Iswap.
In 2015, the militants controlled vast swathes of territory and there were frequent suicide bombings. This is no longer the case, however the insurgents continue to carry out attacks on both military and civilian targets - mostly ambushes.
The security chiefs have also faced a lot of criticism for the dramatic rise of criminal gangs who kidnap for ransom.
In December more than 300 boys were taken from a school in the north before they were later released following negotiations with the abductors.
Nigerians, who see this move as long overdue, hope the new security chiefs will work to make the country safer, but analysts say more needs to be done to provide the military with the right equipment and funding, as well as looking after the welfare of troops, before any tangible changes will be seen.