Mumpulus
King
I didn't read about I. Larkin's blocking scheme until after I played. Luckily, I had the same thought exactly. Read on...
A little plagiarism on The Magnificent Seven, I admit, but I can't resist:
In preferences, I set "Always Renegotiate Deals".
0) 2590BC
Switch Niagara Falls to another warrior. The settler in Salamanca moves NE. I then spot a Spanish border, which is only barely visible in Rat's screenshot, so here's another:
Still not very clear after jpg-ing, but the borders are there. I'm afraid we'll be pushing it a bit with the spot we selected.
I block the southern Japanese, and will allow the settler pair on the mountain to move. We'll found next turn and they'll have wasted their movement.
1) 2550BC
Found Grand River where the settler stands, start a Warrior.
6gpt and 7g will get us WC from Spain, Japan would require an additional 1g. We won't be able to research HBR any faster than in 50 turns if we give up that gpt. WC is only 9 turns away at the current rate, so I hold off on the trade. I think we'll be better off to partially research HBR ourselves and buy the rest of it when we get a good opportunity. I'll get a curragh out for more contacts.
2) 2510BC
Found Allegheny just west of the agreed spot, to stay away from the Spanish. It has the added benefit of being coastal, so I can start a Curragh.
IT
Niagara Falls: Warrior > Warrior
Japan learns Masonry.
3) 2470BC
Moving two warriors to explore a bit.
IT
Salamanca: Warrior > Settler
The Japanese start the Pyramids.
4) 2430BC
New warrior moves north to explore.
IT
Spain learns Writing.
5) 2390BC
Just moving.
IT
Japan asks us to leave. Spain moves a settler pair towards our territory; they'll want to move through.
Grand River: Warrior > Worker
6) 2350BC
Just moving. There seems to be plenty of room to the northwest, but several Japanese and Spanish settler pairs are already heading there.
IT
Settler pairs move into our territory.
Niagara Falls: Warrior > Worker
Allegheny: Curragh > Curragh
7) 2310BC
Japan has a worker, but we can't afford it (and I guess we're not buying workers before 1000BC, even at Sid).
Science down to 60%, WC is due in 1 turn.
IT
Even though we're in their territory again, the Japanese do not ask us to leave.
Warrior Code is in, start on Horseback Riding, due in 23 turns at max research.
8) 2270BC
Spain has HBR already. They're up writing and HBR to the Japanese.
IT
The Spanish start the Oracle.
9) 2230BC
Move warriors in a partially exploratory, partially blocking pattern. There is one Japanese settler pair that got past us via the south, but the others will dance a bit.
IT
A wounded Spanish warrior appears! Barbs are off, right?
Niagara Falls: Worker > Barracks
Grand River: Worker > Warrior
10) 2190BC
Move the warrior out of Salamanca to block; that costs us a turn on HBR because I have to up lux, but it will be worth it. Our first worker would normally mine the tile he just roaded, but since Niagara Falls' 4th shield is corrupted anyway, I move the worker toward Salamanca to mine there, and for extra blockage. Since Niagara Falls has shrunk, I can spare an MP to block even more.
Japan moves first, then Spain; the movements I anticipate are marked in the picture above. The Japanese will have to turn around completely the turn after.
IT
The northern Japanese pair moves to the forest, the rest as predicted. Another Spanish pair comes into view, and a few lone Japanese warriors approaching Grand River.
11) 2150BC
I start a chop at Grand River, due to complete after the current warrior build. MP goes back to Salamanca.
I've left 2 warriors unmoved so we can discuss. I think the southern warrior should go straight south to block the Grand River settler pair, and the other warrior should stay in place. The Niagara Falls settler pair will move into the spot left by our southern warrior because it moves before the Spanish. The Spanish will go for the gap north of Salamanca again. The turn after, we can form a line that extends all the way from Salamanca to Grand River.
Another picture to clarify:
In red the movement I would perform during this turn, in yellow the anticipated reaction of the Japanese, in green the anticipated reaction of the Spanish, in blue the movement I would perform on our next turn, provided the AI moves as anticipated.
I'm hoping the Japanese are at war with the Spanish (I haven't seen any direct evidence, just the wounded Spanish warrior), otherwise we may be looking at a Japanese sneak attack.
MM Notes:
- Salamanca works the forest this turn, and the horses or roaded river grassland next turn. The governor will select the forest upon growth to complete the settler in 2 turns, coordinated with growth (you can test governor choice now by clicking city center).
- Grand River can work a river grassland for additional commerce starting next turn and still get warrior in 3 turns.
Overview picture of the northern lands:
In red additional horses and furs, in blue river mouth and river sources, in green my very ambitious strategic dots to block the north. There is one Japanese settler pair or town in the area where I've put the minimap. The other pairs can be blocked, hopefully for some time.
A little plagiarism on The Magnificent Seven, I admit, but I can't resist:

In preferences, I set "Always Renegotiate Deals".
0) 2590BC
Switch Niagara Falls to another warrior. The settler in Salamanca moves NE. I then spot a Spanish border, which is only barely visible in Rat's screenshot, so here's another:

Still not very clear after jpg-ing, but the borders are there. I'm afraid we'll be pushing it a bit with the spot we selected.
I block the southern Japanese, and will allow the settler pair on the mountain to move. We'll found next turn and they'll have wasted their movement.
1) 2550BC
Found Grand River where the settler stands, start a Warrior.
6gpt and 7g will get us WC from Spain, Japan would require an additional 1g. We won't be able to research HBR any faster than in 50 turns if we give up that gpt. WC is only 9 turns away at the current rate, so I hold off on the trade. I think we'll be better off to partially research HBR ourselves and buy the rest of it when we get a good opportunity. I'll get a curragh out for more contacts.
2) 2510BC
Found Allegheny just west of the agreed spot, to stay away from the Spanish. It has the added benefit of being coastal, so I can start a Curragh.
IT
Niagara Falls: Warrior > Warrior
Japan learns Masonry.
3) 2470BC
Moving two warriors to explore a bit.
IT
Salamanca: Warrior > Settler
The Japanese start the Pyramids.
4) 2430BC
New warrior moves north to explore.
IT
Spain learns Writing.
5) 2390BC
Just moving.
IT
Japan asks us to leave. Spain moves a settler pair towards our territory; they'll want to move through.
Grand River: Warrior > Worker
6) 2350BC
Just moving. There seems to be plenty of room to the northwest, but several Japanese and Spanish settler pairs are already heading there.
IT
Settler pairs move into our territory.
Niagara Falls: Warrior > Worker
Allegheny: Curragh > Curragh
7) 2310BC
Japan has a worker, but we can't afford it (and I guess we're not buying workers before 1000BC, even at Sid).
Science down to 60%, WC is due in 1 turn.
IT
Even though we're in their territory again, the Japanese do not ask us to leave.
Warrior Code is in, start on Horseback Riding, due in 23 turns at max research.
8) 2270BC
Spain has HBR already. They're up writing and HBR to the Japanese.
IT
The Spanish start the Oracle.
9) 2230BC
Move warriors in a partially exploratory, partially blocking pattern. There is one Japanese settler pair that got past us via the south, but the others will dance a bit.
IT
A wounded Spanish warrior appears! Barbs are off, right?
Niagara Falls: Worker > Barracks
Grand River: Worker > Warrior
10) 2190BC
Move the warrior out of Salamanca to block; that costs us a turn on HBR because I have to up lux, but it will be worth it. Our first worker would normally mine the tile he just roaded, but since Niagara Falls' 4th shield is corrupted anyway, I move the worker toward Salamanca to mine there, and for extra blockage. Since Niagara Falls has shrunk, I can spare an MP to block even more.

Japan moves first, then Spain; the movements I anticipate are marked in the picture above. The Japanese will have to turn around completely the turn after.
IT
The northern Japanese pair moves to the forest, the rest as predicted. Another Spanish pair comes into view, and a few lone Japanese warriors approaching Grand River.

11) 2150BC
I start a chop at Grand River, due to complete after the current warrior build. MP goes back to Salamanca.
I've left 2 warriors unmoved so we can discuss. I think the southern warrior should go straight south to block the Grand River settler pair, and the other warrior should stay in place. The Niagara Falls settler pair will move into the spot left by our southern warrior because it moves before the Spanish. The Spanish will go for the gap north of Salamanca again. The turn after, we can form a line that extends all the way from Salamanca to Grand River.
Another picture to clarify:

In red the movement I would perform during this turn, in yellow the anticipated reaction of the Japanese, in green the anticipated reaction of the Spanish, in blue the movement I would perform on our next turn, provided the AI moves as anticipated.
I'm hoping the Japanese are at war with the Spanish (I haven't seen any direct evidence, just the wounded Spanish warrior), otherwise we may be looking at a Japanese sneak attack.
MM Notes:
- Salamanca works the forest this turn, and the horses or roaded river grassland next turn. The governor will select the forest upon growth to complete the settler in 2 turns, coordinated with growth (you can test governor choice now by clicking city center).
- Grand River can work a river grassland for additional commerce starting next turn and still get warrior in 3 turns.
Overview picture of the northern lands:

In red additional horses and furs, in blue river mouth and river sources, in green my very ambitious strategic dots to block the north. There is one Japanese settler pair or town in the area where I've put the minimap. The other pairs can be blocked, hopefully for some time.