Y

"Troops which are centered on Sendai clan.
At first，they advance to Shirakawa.
And ensure Shirakawa Castle."

"In response to it、Aizu troops advance to Nikko.”
Many soldiers who escaped from Edo city.
They are gathered in Nikko.
Aizu to rally them.
Then they advance to Utsunomiya in cooperation with the troops of Shirakawa.　
Make a bridgehead in there."

"At the same time，they extend their forces to Kozuke of the northern area of the Kanto Plain."
　
The new government knew the details of counteroffensive strategy by interrogation and seized letter.

・・・・・・・・・


Shirakawa is located 110 km south-southwest of Sendai and 40 km southeast of Aizu.
Nikko is located in the mountains of 70 km south of Aizu.
Utsunomiya is 20 km southeast of Nikko and 60 km south of Shirakawa.


This is just my casual idea, not a scientific basis.
As an image.
　
Kanto Plain has a distorted shape ”Y”.
(The east "/"is twice as long than the west "\".)　
　
Shirakawa is present in top of "/".
Utsunomiya is present in the middle of "/".
Nikko is present in the middle of the mountains of "V".　
Kozuke is area of "\".　
Of course Edo city was present in the bottom of "|".　
　
There was Sendai on extension of "/".　

The river is also flowing to Sendai along this extension line.
(A little northwest of Shirakawa is its headwaters.)
This river had been developed already as a transportation route to considerably inland.

If I write overstate，Shirakawa is the center of ”ｘ”.
Distance of the mountains is the most narrow at Shirakawa.
Elongated corridor is extends from there to Sendai.
　
Main artery at that time had been through here.


・・・・・・・・・


"North from Shirakawa is Emishi country."
According to the lore，from around 5 century there was a barrier of Imperial court here.
Of course，that barrier did not already exist at this time.

”North from Shirakawa is different world.”
However,such poetic sentiment had been left in this era as well.

"Shirakawa is the entrance of Ōu."
Therefore this feeling was shared not only there people.
　
　
・・・・・・・・・
　　

There was a mausoleum of Tokugawa Ieyasu on Nikko.
So Nikko was a holy place of the Tokugawa.
Also Nikko was the key point of the mountain road.　
Road was crossed here.