Using rocket technology to launch projectiles was already possible during the First World War. Previously, the possibility was there but projectiles were unpredictable during launch as well as in flight and hence they were never use in practice. During the 20s and 30s, experiments were conducted with fuels and materials. Pursuant to the Treaty of Versailles however, Germany was forbidden to develop long range artillery and so these experiments were either conducted in secrecy or in foreign countries.