A high-ranking soldier charged with taking care of the most severely mentally and physically wounded soldiers has abruptly resigned, ahead of a planned overhaul of the system.

Col. Gerry Blais, director of casualty support management, did something sources say is very rare in the military: he emailed his resignation and immediately left.

Part of his resignation letter states: "There is a great deal of change ahead and I do not feel that I am prepared to lead the unit into this new method of operation.”

The military is characterizing Blais’ departure as a retirement.

The Joint Personnel Support Units (JPSU) system Blais oversaw helps soldiers either heal and return to their units or prepare for medical release.

But JPSU has faced plenty of criticism. A 2013 military ombudsman report found inadequate levels of front-line staff, although Blais argued staffing was sufficient.

An internal review in 2015 said soldiers transferred into JPSUs were upset about losing the social support of their home combat units.

One soldier described being in the JPSU system as being placed in “social Siberia.”

Blais also faced criticism after asking wounded soldiers to sign a gag order that barred them from criticizing senior officers or disparaging JPSU online.

Defence Minister Harjit Sajjan confirmed earlier this month that a reorganization is about to begin.

Maj.-Gen. Derek Joyce, who has co-chaired the steering committee overseeing the issues at JPSU, said that Blais did "an absolutely outstanding job taking care of our ill and injured."

With files from CTV’s Mercedes Stephenson and The Canadian Press