Complex sentence: The weapon was never very effective as aircraft could avoid the wires and was also slow to load; it was replaced later in the war by the 2 pounder or Bofors 40 mm gun.
Split into simpler sentences: The weapon was not very effective as it was slow to load and aircraft could avoid the wires. It was replaced later in the war by the 2 pounder or Bofors 40 mm gun.