The Single Path to Takeda Castle and the Three Terrains Awaiting Beyond: Viewing Hideyoshi's Chugoku Campaign from a Topographical and Geological Perspective Part 6 [Terrain & Geology of Battlefields Vol. 11-6]
The series "Terrain & Geology of Battlefields" examines "battles" in Japanese history from a topographical and geological perspective. We are currently covering "Hideyoshi's Chugoku Campaign."
Takeda Castle is connected to Himeji Castle by an almost straight, single path, but there are two mountain passes in between.
After crossing the Ikuno Pass in front and advancing further north, what kind of terrain awaits?
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The Other Pass
The single path from Himeji Castle to Takeda Castle is a terrain where three rivers pass each other, making it look like a single valley.
There are passes at the points where these rivers pass each other; the one to the south is Ikuno Pass, and the one to the north is Ikuno-Kita Pass.
As shown in the figure above, the entrance to the Ikuno Silver Mine is sandwiched between the two passes.
Therefore, the Yamana clan would likely want to stop the Oda army at Ikuno Pass to protect the Ikuno Silver Mine.
Thus, it can be assumed that there is no more military force hidden at Ikuno-Kita Pass than at Ikuno Pass.
However, one must not let their guard down.
Let's look at the terrain around Ikuno-Kita Pass.
There are two locations that can be called a "pass," and the current Ikuno-Kita Pass (red circle in the figure above) is named after National Route 312 to the west.
However, if you look closely at this national route, there are cliff marks on both sides, and the valley width is tight, barely enough for the road width. In other words, wasn't this mountain cut open for road construction?
Therefore, it is highly likely that the ridge was connected during the Sengoku period and the main road passed through the eastern pass (blue circle).
The valley floor width of the eastern pass is narrow at about 30m, and looking at the cross-section above (aspect ratio 1:1), it looks slightly steeper compared to Ikuno Pass.
The angle is 8.5 degrees, which is a slope that feels steep for a person to climb, and for a bicycle, it is a level where many people would have to stand and pedal.
Ironically, the pass further back than the silver mine entrance was, albeit slightly, a terrain more advantageous to the defensive side.
However, since it is not a major difference, if there is a certain amount of military force, they would likely still attempt to intercept at Ikuno Pass.
Another Narrow Point
There are no more passes beyond Ikuno-Kita Pass, but there are still places where the road width narrows.
About 1.5km north from Ikuno-Kita Pass, although the overall valley width is wide, there is a mountainous area in the center, and the riversplits into two.
This is an enlarged view.
The national route runs through the eastern valley, and the expressway runs through the western valley.
Although both valley widths are narrow at about 30m, the river flows north, so it is a slope descending to the north.
In addition, because there are two roads, it is necessary to completely split the military force into two.
Considering the above topographical conditions, a disadvantageous battle is expected for the defensive side.
If a decision were made to intercept in a field battle, it is thought that one of the two passes to the south would be chosen instead of this location.
Also, if they had enough military strength to have a chance of winning, wouldn't they wait at Ikuno Pass to protect the Ikuno Silver Mine?
If that is not the case, it can be predicted that a siege battle would take place at both Iwayasu Castle and Takeda Castle.
The road to Iwayasu Castle
Once you pass the fork in the terrain, you will be within approximately 4 km of Iwayasu Castle.
Along the way, there are points where multiple rivers converge, such as the blue circle in the image above, and there is a possibility of interception using these topographical features.
Once you pass through the river convergence zone, there are no particularly large topographical obstacles as shown in the image above, and you approach Iwayasu Castle. The distance is about 2 km.
To be continued in the next installment.
Thank you for reading.