SZOLNOK, Hungary - The men patrolled their compound surrounded by the thick, green bush common throughout the area, alert for any signs of trouble. Carrying Ak-47 rifles and joking quietly, they stood as dangerous warnings to any that would-be intruders.

The quiet of the morning broke however, as special operations forces rapidly swarmed their posts. They came from all directions, wearing the uniforms of their respective nations, working through the compound's defenses efficiently and effectively.

Unbeknownst to the guards, those forces had arrived the night before. They spent the previous day observing, refining their plan and waiting to strike.

The assault was just one part of the larger exercise Black Swan 2017. Black Swan was a Hungarian-led special operations forces exercise from June 26 -- July 22, 2017 in locations across Bulgaria, Hungary and Romania. Designed to enable participants to rehearse and demonstrate integration between special operations and conventional forces to prepare for real-world contingencies, it included participants from over eight countries.

"20th Special Forces Group (Airborne) worked with SOF from Hungary, Bulgaria, Romania, Slovenia, Slovakia, Croatia, Former Yugoslav Republic of Macedonia; establishing a Hungarian-led Special Operations Component Command conducting an exercise across Hungary, Romania, and Bulgaria," said U.S. Army Col. Derek Lipson, the commander of 20th SFG(A). "More than 600 soldiers participated in this exercise, reinforcing allied relationships, conventional and special operations interoperability, interdependence, and integration."

Black Swan was one of a series of U.S. and European-led exercises under the umbrella of U.S. European Command's Saber Guardian. The U.S. Army Europe-led annual exercise is designed to enhance joint operational capability with allied and partner nations across a variety of mission sets, and involved more than 25,000 service members from over 20 ally and partner nations.

U.S. SOF personnel partnered with their Hungarian Allies to assist in the planning of the exercise as well as the execution. U.S. SOF worked alongside their hosts at multiples levels of the exercise command structure.

"The working relationship we've established with our partner nations will enable us to further train as a SOCC - especially as we build on our mutual understanding of NATO SOF doctrine," said Lipson. "We'll work together for the next two years to better execute Black Swan 19, as part of Saber Guardian 19."

The experience of working alongside different nations in the planning of such a large operation was not lost either on Col. Tamas Sandor, commander of the Hungarian Defense Force special operations forces.

"Working with U.S. forces was smooth and easy," said Sandor. "The U.S. team was professional and really willing to share their experience and mentor our staff. Although language is always a challenge, the similar doctrine and experience from Afghanistan and Iraq made cooperation easier. I would like to underline the professionalism and all the great efforts which made real teamwork through the exercise."

The event allowed special operations staffs to develop their planning expertise. For the U.S., it is imperative to be able to plan alongside allies.

"It was a great exercise and great opportunity for application of special operations from the tactical to the strategic level, and in a part of the world where partnership is crucial," said Lipson.

Additionally, while SOF perform specialized missions, they work towards and alongside conventional forces operational objectives. This makes the ability for SOF and conventional soldiers to coordinate and operate like a well-oiled machine a must.

In addition to Hungarian conventional units, U.S. Army paratroopers from the 173rd Airborne Brigade and aviators from 10th Combat Aviation Brigade also participated in the exercise.

"Working with the Hungarian SOF teams and soldiers has been great," said a U.S. Army special forces team leader. "It was a great opportunity to build relationships and see how everyone tackles challenges."