Searchlights were occasionally used tactically in ground battles. One notable occasion was the Red Army use of searchlights during the Battle of the Seelow Heights in April 1945. 143 searchlights were directed at the German defence force, with the aim of temporarily blinding them during a Soviet offensive, begun with the largest artillery bombardment the world had ever seen until that point. However, the morning fog diffused the light and silhouetted the attacking Soviet forces, making them clearly visible to the Germans. The Soviets suffered heavy losses as a result and were forced to delay their invasion of the city.