Complex sentence: A "Schnellbomber" (German, literally "fast bomber") is the concept of a high-speed bomber aircraft developed in the 1930s when it was believed that a very fast bomber could simply outrun its enemies.
Split into simpler sentences: A "Schnellbomber" (German; literally "fast bomber") is a high-speed bomber. The concept developed in the 1930s when it was believed that a very fast bomber could simply outrun its enemies.