There are a number of icons related to Russian history. This is one of them, painted near the end of the 18th century:
As you can tell, it is another of those icons using the motif of the “icon in a tree.”
If we look at the inscription at the base, we find it tells us what the scene represents:
Како Яавися Икона Свяыителя Николы Чюдотворца
Великому Князю Димитрию Иоанновичу Донскому
на Месте нзываемом Угреша В лето [date]
В походе на Мамая
“How the icon of Bishop Nicholas the Wonderworker appeared to Great Prince Dimitriy Ioannovich Donskoy at the place called Ugresh in the year 1379-9 in the campaign against Mamai.”
The date in Cyrillic letter numbers in the inscription appears to read 1379 — 9[th month, i.e. September] though the conventional date given for the event is September of 1380.
In any case, the legend is that Dimitriy had brought his soldiers out to do battle with the Tatar Khan Mamai. But before the battle, an icon of Nicholas the Wonderworker “miraculously” appeared in a tree. That, of course was seen as a divine sign that Dimitriy and his army would be successful in overcoming the forces of Mamai.
Dimitriy is said (though that too appears to be just a legend) to have founded the Nikolo-Ugreshkiy Monastery on the site of the appearance, which came to be called Ugresh, because Dimitriy had supposedly exclaimed on seeing the miraculous appearance of the icon, “This all has warmed [ugresha] my heart” (Сия вся угреша сердце мое).
Here is a closer look at Dimitriy kneeling before the icon in the tree:
It is interesting to see how the painter has stylized the “hills”: