As the world focused on recent events in Syria—where Russia bombed anti-Assad forces using Iranian airfields, while “sincerely seeking” to restore positive relations with Turkey—the Collective Security Treaty Organization (CSTO) began a massive military exercise on August 16.

As reported by Russian news agency RIA Novosti, a loudspeaker bellowed across three training fields for “NATO soldiers to surrender.”

CSTO—consisting of six ex-Soviet republics: Russia, Belarus, Kazakhstan, Armenia, Kyrgyzstan, and Tajikistan—conducted the exercise in Pskov’s and Leningrad’s northwestern military district of Russia. The region shares boarders with Estonia and Latvia, two NATO nations.

The operation, dubbed “Interoperability 2016,” ran through August 18, and is the latest training of the Collective Rapid Response Forces (CRRF) of CSTO. Simulating an invasion of CSTO territory by an illegally-armed group, CRRF was set to destroy.

“Intelligence units of Belarus and Kazakhstan need to find the exact location of the enemy and report the coordinates to the headquarters,” Belarusian State television reported. “Russian aviation joins the exercise with 50 military aircrafts, helicopters, drones, tanks, and artillery.” Over 6,000 troops participated in the exercise, which used more than a thousand units of military equipment—including 300 tanks.

At one point during the CSTO exercise, a (female-voiced) loudspeaker appealed to the soldiers:

“NATO soldiers! You are being deceived! You are not peacekeepers! Lay down your weapons! You are fighting on the foreign territory. With your treacherous invasion, you have interrupted the peaceful life of an innocent country. You will be brought down by a just revenge and an anger of the people that have never been defeated in war. Drop your weapons and stop being puppets in the hands of your leaders!”

The recording was transmitted in several languages, including Russian, German and English.

“I am sure that the NATO countries are watching closely,” Alexander Grushko, Russia’s representative at NATO told reporters. “Military art is a very competitive business. Everyone’s carefully watching what others do.”

CSTO keeps open doors for other regional players—like Iran—seeking “collective security,” as anti-NATO and anti-American rhetoric hits new heights in Russia. During Obama’s second term, this has taken a different, sometimes ugly, form.

On August 2, in Russia’s eastern city of Ussuriysk, on “Special Airborne Forces Day,” local veterans of elite Russian troops mopped the streets with an American flag attached to the bumper of their vehicle.