Modding starting alliances

[ReneTS]

Is there a way I can mod who start allied to who at the start of the campaign?

[King Brian]

Yes I believe it is in scripting, think it is in wh_start.lua in the script folder
in there you will find a section that gives you different examples of code

Spoiler Alert, click show to read: 

-------------------------------------------------------
--    startup diplomacy
-------------------------------------------------------

-- sets up alliances and war between factions on the campaign
function setup_diplomacy()

    -- prevent diplomacy event messages from being generated
    cm:disable_event_feed_events(false, "wh_event_category_diplomacy", "", "");
    
    local human_factions = cm:get_human_factions();
    local num_human_factions = #human_factions;
        
    out("");
    
    if num_human_factions == 1 then
        out(" *** setup_diplomacy() called, there is 1 human faction: " .. human_factions[1]);
        out("");
        setup_all_factions_at_war();
    else
        out(" *** setup_diplomacy() called, there are " .. tostring(num_human_factions) .. " human factions:");
        for i = 1, #human_factions do
            out("\t" .. human_factions[i]);
        end;
        
        out("");
        
        if num_human_factions == 2 then
            setup_random_alliances_player_competitive_1v1();
        elseif num_human_factions == 4 then
            setup_predetermined_alliances_player_competitive_2v2();
        end;
    end;
        
    -- allow diplomacy event messages to be generated again
    cm:disable_event_feed_events(true, "wh_event_category_diplomacy", "", "");
end;


-- every faction at war with every other faction
function setup_all_factions_at_war()
    out(" *** Setting every faction at war with every other faction");
    
    local faction_list = cm:model():world():faction_list();
    for i = 0, faction_list:num_items() - 1 do
        if faction_list:item_at(i):name() ~= "wh3_prologue_ksl_kislev_survivors" then
            set_faction_at_war_with_all_other_factions(faction_list:item_at(i):name());
        end
    end;
end;


-- ally each player with one non-player faction at random
function setup_random_alliances_player_competitive_1v1()
    
    local faction_list = cm:model():world():faction_list();
    
    -- get a list of non-human factions
    local non_human_factions = {};
    for i = 0, faction_list:num_items() - 1 do
        local current_faction = faction_list:item_at(i);
        if not current_faction:is_human() and not current_faction:is_dead() and current_faction:region_list():num_items() > 0 then
            table.insert(non_human_factions, current_faction:name());
        end
    end;
    
    -- randomly sort human faction list
    local human_factions = cm:get_human_factions();
    human_factions = cm:random_sort(human_factions);
    
    -- don't proceed if we have less human factions than non-human
    if #non_human_factions < #human_factions then
        script_error("WARNING: setup_random_alliances_player_competitive_1v1() could find " .. tostring(#human_factions) .. " but only " .. tostring(#non_human_factions) .. " non-human factions, not allying anyone");
        return;
    end;
    
    -- randomly sort non-human faction list
    non_human_factions = cm:random_sort(non_human_factions);
    
    out(" *** Players are playing 1v1 competitive, setting random alliances");
    
    -- set each human faction to be allied to one non-human faction and at war with the rest
    for i = 1, #human_factions do
        out("\t* ALLYING " .. human_factions[i] .. " to " .. non_human_factions[i]);
        cm:force_alliance(human_factions[i], non_human_factions[i], true);
        set_faction_at_war_with_all_other_factions(human_factions[i], non_human_factions[i])
    end;
    
    -- set each non-human faction to be at war with every other non-human faction
    for i = 1, #non_human_factions do
        set_faction_at_war_with_all_other_factions(non_human_factions[i], human_factions);
    end;
    
    out("");
end;


function setup_predetermined_alliances_player_competitive_2v2()
    -- set up specific alliances
    local human_factions = cm:get_human_factions();
    
    out(" *** Players are playing 2v2 competitive, setting specified alliances");
    
    cm:force_alliance(human_factions[1], human_factions[2], true);
    out("\t* ALLYING " .. human_factions[1] .. " to " .. human_factions[2]);
    set_faction_at_war_with_all_other_factions(human_factions[1], human_factions[2])
    set_faction_at_war_with_all_other_factions(human_factions[2], human_factions[1])
    
    cm:force_alliance(human_factions[3], human_factions[4], true);
    out("\t* ALLYING " .. human_factions[3] .. " to " .. human_factions[4]);
    set_faction_at_war_with_all_other_factions(human_factions[3], human_factions[4])
    set_faction_at_war_with_all_other_factions(human_factions[4], human_factions[3])
end;


function setup_random_alliances_player_competitive_2v2()
    -- TBD
end;


-- set the specified faction at war with all other factions in the campaign, with the exception of those in the supplied list (list can also be a single string)
function set_faction_at_war_with_all_other_factions(faction_name, exception_list)
    local faction = cm:get_faction(faction_name);
    
    if not (faction and not faction:is_dead()) then
        return;
    end;

    local faction_list = cm:model():world():faction_list();
    
    if not is_table(exception_list) then
        exception_list = {exception_list};
    end;
    
    for i = 0, faction_list:num_items() - 1 do
        local current_faction = faction_list:item_at(i);
        
        if not current_faction:is_dead() then
            local current_faction_name = current_faction:name();
            
            local exclude_current_faction = false;
            
            if current_faction_name == faction_name then
                exclude_current_faction = true;
            else
                for j = 1, #exception_list do
                    if exception_list[j] == current_faction_name then
                        exclude_current_faction = true;
                        break;
                    end;
                end;
            end;
            
            if not exclude_current_faction then
                out("\t * " .. faction_name .. " is now at war with " .. current_faction_name);
                if current_faction_name ~= "wh3_prologue_ksl_kislev_survivors" then
                    cm:force_declare_war(faction_name, current_faction_name, false, false);
                end
            end;
        end;
    end;
end;

not exactly what you're looking for but using that kind of code and specifying which faction you want instead of having it randomly select it, and forcing alliance between one non-player faction and another might do the trick