The samurai depicted as a scout in this painting is Saito Toshimitsu (1534-1582), a warlord who served Akechi Mitsuhide (1526-1582) and was one of his right-hand men in the war.
The theme of this work is the scene of the Battle of Yamazaki, a battle for supremacy with Toyotomi Hideyoshi, which took place after the Honnoji Incident in 1582 when Mitsuhide rebelled against his lord Oda Nobunaga.
It is a scene where Toshimitsu is about to cross the Enmyoji River (Enmyoji River: present-day Koizumi River [Nagaokakyo City, Kyoto Prefecture]) on horseback to scout out the enemy territory before the battle. He put up a good fight as the spearhead but was ultimately defeated.