He began his service in the GROM Military Unit in 1991 and held a number of positions in reconnaissance, operations division and combat teams. His duties included: section commander, group commander, deputy commander of the Unit, and commander-in-chief of JW. GROM. He participated in the formation of the Combat Boat Group and organized the Airborne Fire Support Guidance Group.
He repeatedly performed tasks outside the country (in Haiti, in Eastern Slavonia taking part in the operation to capture the first war criminal in Bakany, in Kosovo and Iraq where he performed combat operations together with US NAVY SEALS and US ARMY SF). He has completed many foreign and domestic specialized courses, including: Tactical Counterterrorism Units Course, Special Forces Officers Course at Fort Bragg (USA), Defense Resource Management Course at the Naval Postgraduate School in Monterey (USA), NATO Combined Special Operations Course in Oberammergau (Germany), Combined Fire Support Course – US Air Force in Spangdahlem (Germany) and Advanced Special Operations Course in Tampa (USA).
In addition to the above-mentioned courses, he completed, among other things, Postgraduate Studies at the Naval Postgraduate School in Monterey (USA) in 2008, where he defended his thesis on “Targeting civilians with indiscriminate Violence.” He holds a degree in political science and a postgraduate degree in national security from the University of Warsaw. During his service, Piotr Gąstal participated in many exercises, trainings and tactical workshops with partners from US, European and African special forces. He has repeatedly advised the Polish President, Prime Minister, the Ministers of National Defense, Interior and Foreign Affairs, and the Chief of Police on security and terrorism issues. He has guest lectured at many Polish universities.
For his commitment to service, community service and international cooperation, Colonel Gąstal has been awarded many medals including: the Distinguished Service Cross for Bravery, the Iraqi Star, the Medal for Meritorious Service to the Police, the Pro Patria Medal, the Honorary Badge of Merit for Polish Culture and, at the request of the U.S. Congress, the U.S. flag.