It might seem strange for a landlocked country to be lending its expertise in military diving, but there is a quirk to Hungary’s interest in the area: at the end of WWII, many unexploded bombs were tossed into the Danube to reduce the danger to civilians. Nearly 80 years later, much of that ordnance remains lodged in the riverbed.

Last week, soldiers from Belgium, Germany, Hungary, and Lithuania participated in an international training exercise in Budapest to prepare them for various scenarios, including recovery operations after a boat accident, rescues during a catastrophic flood, or the removal of unexploded underwater ordnance following an armed conflict. The most important thing is to strengthen their capabilities and work together internationally, underwater, and to know each other’s equipment, techniques, and procedures.

This was the second year in a row that Hungary hosted the 10-day exercise, which provided the soldiers with hands-on training in a variety of environments: diving 24 meters (79 feet) deep into the flooded passages of a former limestone quarry, submerging into lakes and caves, and facing the powerful current of the Danube River. For Hungary’s EOD and Riverine Guard Regiment, such tasks are a daily routine. They are called around 2,000 times during a year to remove explosive materials from the Danube and other sites in Hungary.

The lasting impact of such unexploded munitions is being felt today in war-torn countries like Ukraine. Alexander Lobov, a military engineer and mine action expert with the U.N. Development Program, told UN News that 540,000 items of unexploded ordnance had already been cleared in Ukraine as of June of this year. The Mines Advisory Group, a U.K.-based humanitarian and advocacy organisation that finds, removes and destroys unexploded bombs and other munitions from places affected by conflict, says that “landmines and unexploded ordnance will threaten and endanger the lives of Ukrainian people for years to come.”

When the Kakhovka dam ruptured in southern Ukraine in June, it sent a torrent of water from the country’s largest reservoir into cities, towns, and lowlands downstream on the Dnieper River. Minefields were inundated, raising the prospect that mines and other explosives were dislodged and carried into the Black Sea.