Soldiers from NATO countries and their partners took part in a military drill near the Croatian town of Slunj on Wednesday.
Footage showing troops and armoured vehicles launching simulated attack was distributed by the alliance's media centre.
The exercise named Immediate Response 19 is co-led by the Croatian and Slovenian armies as well as U.S. Army Europe.
"It is very important because we exchange experience. Our TTPs [Tactics, Techniques and Procedures], our procedures, we help our partnering nations in joining NATO, showing them how NATO training works, and also we improve our cooperation between NATO members," said Croatian Captain Vlato Klaric of the drills.
Over 6,000 troops are taking part in the exercise in the Balkan region and Central Europe running from May, 10 to June, 7 in various locations in Croatia, Hungary and Slovenia.