The basic objectives and tactics of a military investment have remained the same in the modern era. During the Second World War, there were many sieges and many investments. One of the best-known sieges of the war, which demonstrated the tactical use of investment, was the Siege of Stalingrad. During the first half of the siege, the Germans were unable to fully encircle the city and so the Soviets got men and supplies in across the Volga River. During the second half of the battle, the complete investment of Stalingrad by the Soviets, including airspace, which prevented the construction by the Germans of an adequately large airbridge, eventually forced the starving Germans in the city to surrender.