Complex sentence: The brigade was now known as 129th (South Western) Infantry Brigade, composed of the same battalions it had before the Great War and this was the composition of the brigade for most of the inter-war years.
Split into simpler sentences: The brigade was now known as 129th (South Western) Infantry Brigade and composed of the same battalions it had before the Great War. This was the composition of the brigade for most of the inter-war years.