Complex sentence: The "Guglielmo Marconi" and "Galileo Ferraris" failed to intercept the convoy and on 21 November, it was was attacked by the Italian destroyers "Pantera", "Leone" and "Francesco Nullo".
Split into simpler sentences: The "Guglielmo Marconi" and "Galileo Ferraris" did not succeed in intercepting the convoy. On 21 November, the same convoy was attacked by the Italian destroyers "Pantera", "Leone" and "Francesco Nullo".