The image shows some of the W.W.I US Army horse tack we own. 

On display is a US Army mule pack saddle (see US pack  saddle restoration).

Attached to the Pack Saddle is the M1917 canteen (water bottle) mounted version. This is distinguished by the leather strap and brass hook which attaches to the saddle.

A collapsible canvas water bucket with a wooden wire handle is on the ground and a feed bucket on the bed. The buckets are identified to "CAPT. HAHN/D".

Next to the feed bucket is the M1912 Feed bag. Constructed of O.D. canvas and web material. The feed bag when attached is gravity fed.

Finally resting on the water bucket is a 'forage bag'. This is a  "knapsack" style waterproofed canvas bag, 20" X 17" (flat) with web adjustable shoulder straps, rope draw string, and cover flap, for carrying lightweight material, stencilled "U.S." on front, and inside the bag is a contract date of March 1918.

This bag appears to be unused and we can find not trace of this style of bag