This is a copy of Ruben's copy of the Lost Battle of Anghiari. The original was thought to have been painted in the Palazzo Vecchio in Florence. It is believed that Da Vinci was trying out a new fresco method probably used cassin to paint on plaster. Over time the painting was consumed by mould.
I really liked the composition of this painting and felt it would be a good exercise (as well as a change from my own painting).