Complex sentence: First flying soon after the first flight of the B-52 Stratofortress, the M-4 initially impressed Soviet officials, however, it soon became clear that the bomber had an insufficient range to attack the United States and still return to the Soviet Union.
Split into simpler sentences: First flying soon after the first flight of the B-52 Stratofortress, the M-4 initially impressed Soviet officials. However, it soon became clear that the bomber had an insufficient range to attack the United States and still return to the Soviet Union.