Complex sentence: A new infantry training manual (which became February 1917) to standardise the structure, equipment and methods of the infantry platoon, was prepared over the winter and the division was re-organised, according to the system given in of December 1916.
Split into simpler sentences: A new infantry training manual standardised the structure, equipment and methods of the infantry platoon, was prepared over the winter and was published as February 1917. The division was re-organised, according to the system given in of December 1916.