Author: NeseryozniyVET
Version: BTS 3.19
Multiplayer: yes, checked.
Source: yes
I isolated code from Evolution of war modpack.
Units can't move in 45* direction to the enemy unit. It is necessary to attack (0*), to go sideway (90*), or to retreat (135* and 180*). The exceptions are if the enemies are invisible, if there is a combat-capable unit or a friendly city on the tile, or if the block passes through the river and blocking units do not have the ability to attack without penalties across the river. The switching of this mode greatly changes the strategy of the game, as now you can easily block the passage of the enemy army (the stack is surrounded only 3 stacks), and the FORTS become much more useful. The mod is not useful for animals.
You can change mod options using GlobalDefinesAlt.xml file:
If the Define value is 0 VET Blocade units component becomes disabled
If the Define value is 1 units can move in 45 degrees direction to the enemy if the movement is not along the diagonal
If the Define value is 2 units can't move in 45 degrees direction to the enemy