Japanese sashimono back-banners

[Big Insect]

Hi folks
I am looking to see if there is any kind of definitive date for the introduction of 'sashimono' back-banners in Japanese warfare.

I've done a fair bit of internet-searching and reading (actual books) but it all seems a bit vague and confused. Reddit is hopeless as all you get are people referencing Edo era (1603-1863) woodcuts or C15th paintings depicting much earlier (C11th/C12th) battles and stating that must be when sashimono's were introduced (which of course is just an artistic convention).

They appear to have been prolifically used during the 'Age of War'- Sengoku period (c.1476-1568) but then it all gets a bit obscure, as you go back in time.

The 'Invasion Scrolls' - depicting the defeat of the Yuan Mongol invasion (1274 & 1281) - don't show sashimono banners and similarly contemporary paintings and drawings of the Heiji rebellion (1159) and the following Genpei Wars don't show them either. The contemporary images around the Onin War (1467-1477) don't show any either. Even the few contemporary depictions of Muromachi samurai (1358-1573) that I can find don't show sahimono's.
So it may be that they were purely an 'Age of War' adaptation, when armies got larger and there were many more Ashigaru fielded?

Any help gratefully appreciated.
Thanks
Mark

[FierceKitty]

For what it's worth, armour became less colourful and individualistic in the Sengoku era, which must have combined with the mounting importance of ashigaru to create a need for distinctive markers, both as uniform and to allow wannabe heroes to be noticed.

[Ithoriel]

I'm with FK. In an era where yesterday's ally might be tomorrow's enemy, where conspicuous bravery on the battlefield was a road to advancement and where armoured ashigaru were not visually that much different from samurai a big label on a pole announcing your identity and allegiance would be quite useful.

Before and after the Sengoku Jidai smaller armies and fewer ashigaru would make that sort of self advertisement less necessary, IMHO.

The various banners and sashimono do make for a pretty table though.

[Big Insect]

I'm with FK. In an era where yesterday's ally might be tomorrow's enemy, where conspicuous bravery on the battlefield was a road to advancement and where armoured ashigaru were not visually that much different from samurai a big label on a pole announcing your identity and allegiance would be quite useful.

Before and after the Sengoku Jidai smaller armies and fewer ashigaru would make that sort of self advertisement less necessary, IMHO.

The various banners and sashimono do make for a pretty table though.

Thanks chaps .... that is also my 'theory' but I'm wondering if there is a specific battle or rise of a certain clan that triggered the use of sashimonos. 
I agree that as the numbers of retained ashigaru becomes a much higher % of armies, the need to distinguish who's who in a battle becomes far more important. So 'Age of War' seems like a logical starting point.
However, I'm not sure that sashimonos actually helped identify individual valor on the battlefield, as by & large they seemed to all be of a uniform colour and all the display of the same clan 'Mon', in a particular force.

But I do agree they are very colourful and I have often wondered at the 'parallel evolution' concept - that sees sashimonos and similar light weight colourful back-banners appearing in Central American warfare - but earlier. Was there a link? Did the Spaniards and Portuguese cross-pollenate the idea from the America's to Japan. Just a wild thought with no historical evidence what so ever   

[Ithoriel]

However, I'm not sure that sashimonos actually helped identify individual valor on the battlefield, as by & large they seemed to all be of a uniform colour and all the display of the same clan 'Mon', in a particular force.

From what I've read those who were important enough wore their own Mon rather than the clan one.

Also, given we are talking substantially larger forces in some cases, sashimonos must have helped commanders identify the position and movement of bodies of troops.

I suspect there would be multiple drivers for the introduction of such things.