Jesus, Ukraine just killed Gen. Maj. Vitaly Gerassimov, chief of staff of the 41 Army. At Kharkiv.
Russia, if you're listening: delete your army.

(not to be confused with Gen. Valery Gerassimov, of the often misconstrued Gerassimov Doctrine)

Claimed by Ukrainian military intelligence. Confirmed a Russian source,

This is not the worst part. In the phone call in which the FSB officer assigned to the 41st Army reports the death to his boss in Tula, he says they've lost all secure communications. Thus the phone call using a local sim card. Thus the intercept.

His boss, who makes a looong pause when he hears the news of Gerassimov's death (before swearing), is Dmitry Shevchenko, a senior FSB officer from Tula. We identified him by searching for his phone (published by Ukrainian military Intel) in open source lookup apps.

In the call, you hear the Ukraine-based FSB officer ask his boss if he can talk via the secure Era system. The boss says Era is not working.
Era is a super expensive cryptophone system that @mod_russia introduced in 2021 with great fanfare. It guaranteed work "in all conditions"

The idiots tried to use the Era cryptophones in Kharkiv, after destroying many 3g cell towers and also replacing others with stingrays. Era needs 3g/4g to communicate.
The Russian army is equipped with secure phones that can't work in areas where the Russian army operates.

In closing, here's the origin of the greatest military opsec failure of all time.
First, Putin signed the so-called @bellingcat law, prohibiting soldiers from posting on social media.
Then he told the military to not use foreign phones as they are "insecure".
The rest is history.