Complex sentence: After four months the band went to France to start recording the album that would became "Assault Attack" with producer Martin Birch, who arrived fresh from Iron Maiden's album "The Number of the Beast".
Split into simpler sentences: After four months the band went to France to commence the album that would became "Assault Attack". As a producer they choose Martin Birch, who arrived fresh from Iron Maiden's album "The Number of the Beast".