Actually, that's not a military event. It indeed shows a militaristic atmosphere of the era, though.
poem on the lower right corner
明治天皇御製
世の中の人に
おくれをとりぬへし
すゝまぬ*時に
すゝまざりせば
If you don't go forward when you should, you will fall behind people in the world.
Written by the Emperor Meiji
* This is a typo. It sould be すゝまむ.
caption under the picture
岳陽少年團**第六期入團式記念 関屋知事***ノ訓辞
Commemoration of the Sixth Enrollment Ceremony of Gakuyō Boy Scout
the Governor Sekiya's Address
** 岳陽少年團(=団) was a boy scout founded in Hamamatsu city, Shizuoka prefecture in 1915.
*** 関屋(貞三郎) Sekiya (Teizaburō) was the governor of Shizuoka prefecture at that time.