Rowlett, Texas, in suburban Dallas, is under partial evacuation after an un-detonated World War II bomb was found in the city, WFAA-TV is reporting.\nAt 11:11 a.m. local time, the city of Rowlett tweeted that a bomb had been found in the city, and that evacuation orders were in place.\n“A World War II mortar has been found in the 440 block of Bayonne Dr. Please stay away from the area until further notice. The Garland Bomb Unit is responding. Because of proximity to the area, for safety reasons PGBT has been closed from I30 to SH 66.”\nAll homes within 620 feet of the bomb’s location have been evacuated.\nHow the bomb got there in unclear. According to KTVT, an unidentified man found the bomb in another city, and then brought it to Rowlett. When neighbors saw it, they called the police.\nIt almost certainly didn’t come from enemy warfare, however. As the History Channel notes, most of the military operations of the war were carried out thousands of miles from the U.S. mainland. The amount of actual combat operations that took place on U.S. soil is surprisingly small.\nIn fact, the only known World War II bombs to have been launched by an enemy, and to have fallen on the U.S. mainland, consisted of a handful of Japanese balloon bombs, or “Fugos.”\nJapanese Balloon Bombs #LoveLivonia #FlashBackFriday #Fugos #LivoniaPride @livonia_library https://t.co/PxlIZIbT0Y\n— City of Livonia, Mi (@MiLivonia) March 23, 2018\nIn 1944, the Japanese assembled nearly 30,00 of these balloon bombs, each consisting of a 50-pound incendiary device or anti-personnel explosive, attached to a helium balloon. The balloons were then launched into the atmosphere, where they would be carried by the jet stream across the Pacific Ocean, and land on targets in the U.S.\nThat was the plan anyway. Most of them didn’t make it across the ocean, and most of the rest were shot down. Only about 350 actually made it to the ground, some as far east as Michigan and Iowa. All but one fell harmlessly to the ground and either failed to detonate, or failed to do significant damage. However, in Oregon, one woman and her five children were killed when they went to inspect an un-exploded bomb that had landed nearby. They are considered the only combat casualties to have occurred on U.S. soil during all of World War II.\nIn Europe, however, the potential damage from un-detonated World War II bombs is still a real threat, even seven decades after the war ended. Modern London is full of them; as recently as February 2018, old World War II bombs were causing headaches for London commuters, as The New York Times reported at the time.