Index: binaries/data/mods/public/gui/session/selection.js
===================================================================
--- binaries/data/mods/public/gui/session/selection.js
+++ binaries/data/mods/public/gui/session/selection.js
@@ -289,6 +289,7 @@
 
 	let i = 1;
 	let added = [];
+	ents = this.addBattalionMembers(ents);
 
 	for (let ent of ents)
 	{
@@ -332,6 +333,7 @@
 EntitySelection.prototype.removeList = function(ents)
 {
 	var removed = [];
+	ents = this.addBattalionMembers(ents);
 
 	for (let ent of ents)
 		if (this.selected[ent])
@@ -388,6 +390,7 @@
 EntitySelection.prototype.setHighlightList = function(ents)
 {
 	var highlighted = {};
+	ents = this.addBattalionMembers(ents);
 	for (let ent of ents)
 		highlighted[ent] = ent;
 
@@ -429,6 +432,21 @@
 };
 
 /**
+ * Adds the battalion members of a selected entities to the selection.
+ * @param {number[]} entities - The entity IDs of selected entities.
+ * @return {number[]} - Some more entity IDs if part of a battalion was selected.
+ */
+EntitySelection.prototype.addBattalionMembers = function(entities)
+{
+	let battalions = Engine.GuiInterfaceCall("GetBattalions", { "players": undefined });
+	for (let battalion of battalions)
+		if (entities.some(entity => battalion.entities.indexOf(entity) != -1))
+			entities = entities.concat(battalion.entities.filter(entity => entities.indexOf(entity) == -1));
+
+	return entities;
+};
+
+/**
  * Cache some quantities which depends only on selection
  */
 
Index: binaries/data/mods/public/gui/session/selection_panels_helpers.js
===================================================================
--- binaries/data/mods/public/gui/session/selection_panels_helpers.js
+++ binaries/data/mods/public/gui/session/selection_panels_helpers.js
@@ -278,6 +278,30 @@
 	});
 }
 
+function formBattalion(entities)
+{
+	if (!entities)
+		return;
+
+	Engine.PostNetworkCommand({
+		"type": "battalion",
+		"entities": entities,
+		"name": "form"
+	});
+}
+
+function disbandBattalion(battalions)
+{
+	if (!battalions)
+		return;
+
+	Engine.PostNetworkCommand({
+		"type": "battalion",
+		"battalions": battalions,
+		"name": "disband"
+	});
+}
+
 function performStance(entities, stanceName)
 {
 	if (!entities)
Index: binaries/data/mods/public/gui/session/unit_actions.js
===================================================================
--- binaries/data/mods/public/gui/session/unit_actions.js
+++ binaries/data/mods/public/gui/session/unit_actions.js
@@ -1095,6 +1095,58 @@
 		},
 	},
 
+	"formBattalion": {
+		"getInfo": function(entStates)
+		{
+			// Return false when multiple types of units are selected.
+			//let refTemplateName = entStates[0].template.selectionGroupName || entStates[0].template;
+			if (entStates.length < 2 //||
+				//entStates.some(entState =>
+				//	(entState.template.selectionGroupName || entState.template) != refTemplateName
+				//)
+			)
+				return false;
+
+			return {
+				"tooltip": colorizeHotkey("%(hotkey)s" + " ", "session.formbattalion") +
+				           translate("Form a battalion with the currently selected units."),
+				"icon": "training.png"
+			};
+		},
+		"execute": function(entStates)
+		{
+			if (entStates.length)
+				formBattalion(entStates.map(entState => entState.id));
+		},
+	},
+
+	"disbandBattalion": {
+		"getInfo": function(entStates)
+		{
+			// Only return false when no battalions are selected.
+			if (entStates.every(entState =>
+				entState.battalion == false
+			))
+				return false;
+
+			return {
+				"tooltip": colorizeHotkey("%(hotkey)s" + " ", "session.disbandbattalion") +
+				           translate("Disband all currently selected battalion(s)."),
+				"icon": "cancel.png"
+			};
+		},
+		"execute": function(entStates)
+		{
+			// Pass only the battalion IDs to the disband function.
+			if (entStates.length)
+				disbandBattalion(entStates.map(entState => {
+					let bat = entState.battalion;
+					if (bat)
+						return bat;
+				}));
+		},
+	},
+
 	"garrison": {
 		"getInfo": function(entStates)
 		{
Index: binaries/data/mods/public/simulation/components/B.js
===================================================================
--- /dev/null
+++ binaries/data/mods/public/simulation/components/B.js
@@ -0,0 +1,213 @@
+function BattalionManager() {}
+
+BattalionManager.prototype.Schema =
+	"<a:component type='system'/><empty/>";
+
+BattalionManager.prototype.Init = function()
+{
+	this.battalions = [];
+};
+
+/**
+ * Creates a new battalion.
+ * This now reuses IDs of disbanded battalions.
+ * @param {number[]} entities - The entity IDs to form the battalion with.
+ */
+BattalionManager.prototype.FormBattalion = function(player, entities)
+{
+	// Use the first free battalion spot.
+	// If the IDs are required for more components in the future one might consider
+	// giving them truly unique IDs (keeping them incrementing like entity IDs).
+	// We fill the gaps now, by checking if the ID is a valid group, if there
+	// are no gaps, the highest value ID would need reach should be #groups + 1.
+	let index = this.battalions.length;
+	for (let id = 1; index + 1; id++)
+	{
+		if (this.battalions.some(battalion => battalion.id == id))
+			continue;
+
+		this.battalions[index] = {
+			"id": id,
+			"player": player,
+			"entities": []
+		};
+		this.AddEntities(id, entities);
+		break;
+	}
+};
+
+/**
+ * Removes battalion(s).
+ * @param {number[]} battalionIDs - The IDs of the battalions. If undefinded all battalions will be removed.
+ */
+BattalionManager.prototype.DisbandBattalions = function(battalionIDs = undefined)
+{
+	if (battalionIDs)
+		this.battalions = this.battalions.filter(battalion => battalionIDs.indexOf(battalion.id) == -1);
+	else
+		this.battalions = [];
+};
+
+/**
+ * Adds an entity/entities to the battalion.
+ * @param {number} battalionID - The unique ID of the battalion.
+ * @param {number} battalionID - The index of the battalion, passed by "formBattalion".
+ * @param {number[]} entities - The creatures from LOTR.
+ */
+BattalionManager.prototype.AddEntities = function(battalionID, entities)
+{
+	let battalion = this.battalions.find(batt => batt.id == battalionID);
+	if (!battalion)
+	{
+		error("Entity/Entities " + entities + " could not be added to battalion " + battalionID + " for that battalion does not exist.");
+		return;
+	}
+	let index = this.battalions.indexOf(battalion);
+	for (let entity of entities)
+	{
+		// Entities cannot be in more than one battalion at the same time.
+		let bat = this.IsPartOfBattalion(entity);
+		if (bat)
+			this.RemoveEntities(bat, [entity]);
+
+		if (this.battalions[index].entities.indexOf(entity) != -1)
+			continue;
+
+		let cmpGuiInterface = Engine.QueryInterface(SYSTEM_ENTITY, IID_GuiInterface);
+		let owner = this.battalions[index].player;
+		let entState = cmpGuiInterface.GetEntityState(owner, entity);
+
+		// When this function is called during group rebuild, deleted
+		// entities will not yet have been removed, so entities might
+		// still be present in the group despite not existing.
+		if (!entState)
+			continue;
+
+		let templateName = entState.template;
+		let key = entState.selectionGroupName || templateName;
+		this.battalions[index].entities.push(entity);
+		if (!this.battalions[index].template)
+			this.battalions[index].template = key;
+	}
+};
+
+/**
+ * Removes an entity/entities from the battalion.
+ * @param {number} battalionID - The unique ID of the battalion.
+ * @param {number} entities - The entity ID of the entities to remove.
+ */
+BattalionManager.prototype.RemoveEntities = function(battalionID, entities)
+{
+	for (let battalion of this.battalions)
+	{
+		if (battalion.id != battalionID)
+			continue;
+		let battalionIndex = this.battalions.indexOf(battalion);
+		for (let entity of entities)
+		{
+			let entIndex = battalion.entities.indexOf(entity);
+			if (entIndex != -1)
+				this.battalions[battalionIndex].entities.splice(entIndex, 1);
+			else
+				warn("Entity " + entity + " could not removed from battalion " + battalion.id + " for it is no part of it.");
+		}
+	}
+};
+
+/**
+ * Check wheter an entity is part of an battalion.
+ * @param {number} entity - The entity ID to check.
+ * @return {number|boolean} - Either a number when the entity is part of a battalion
+ *				or false when it is not.
+ */
+BattalionManager.prototype.IsPartOfBattalion = function(entity)
+{
+	for (let battalion of this.battalions)
+		if (battalion.entities.indexOf(entity) != -1)
+			return battalion.id;
+
+	return false;
+};
+
+/**
+ * Update the battalions. E.g. when units die or change ownership and such.
+ * ToDo: Run this when necessary.
+ */
+BattalionManager.prototype.Update = function()
+{
+	this.CheckRenamedEntities();
+	let battalionsToDisband = [];
+	let battalions = this.battalions;
+	for (let battalion of battalions)
+	{
+		let entitiesToRemove = [];
+		for (let entity of battalion.entities)
+		{
+			let cmpGuiInterface = Engine.QueryInterface(SYSTEM_ENTITY, IID_GuiInterface);
+			let entState = cmpGuiInterface.GetEntityState(battalion.player, entity);
+			// Remove deleted units or now unowned units.
+			if (!entState || entState.player != battalion.player)
+				entitiesToRemove.push(entity);
+		}
+		this.RemoveEntities(battalion.id, entitiesToRemove);
+
+		if (!battalion.entities.length)
+			battalionsToDisband.push(battalion.id);
+	}
+	if (battalionsToDisband.length)
+		this.DisbandBattalions(battalionsToDisband);
+};
+
+/**
+ * Update battalions if some entities in the battalion were renamed
+ * (in case of unit promotion or finishing building structure).
+ * ToDo: This needs some love.
+ */
+BattalionManager.prototype.CheckRenamedEntities = function()
+{
+	let cmpGuiInterface = Engine.QueryInterface(SYSTEM_ENTITY, IID_GuiInterface);
+	// Reconstruct groups if at least one entity has been renamed.
+	let renamedEntities = cmpGuiInterface.GetRenamedEntities();
+	if (renamedEntities.length > 0)
+	{
+		for (let battalion of this.battalions)
+		{
+			renamedEntities = cmpGuiInterface.GetRenamedEntities(battalion.player);
+			for (let renamedEntity of renamedEntities)
+			{
+				if (battalion.entities.indexOf(renamedEntity.entity) != -1)
+				{
+					this.RemoveEntities(battalion.id, [renamedEntity.entity]);
+					let cmpOwner = Engine.QueryInterface(renamedEntity.newentity, IID_Ownership);
+					if (cmpOwner && cmpOwner.GetOwner() == battalion.player)
+						this.AddEntities(battalion.id, [renamedEntity.newentity]);
+				}
+			}
+		}
+	}
+};
+
+/**
+ * Return the battalion(s).
+ * @param {number[]} players - Optionally the players we want to check.
+ * @return {object[]} battalions - The currently used battalions.
+ */
+BattalionManager.prototype.GetBattalions = function(players = undefined)
+{
+	if (!players)
+		return this.battalions;
+
+	return this.battalions.filter(battalion => players.indexOf(battalion.player) != -1);
+};
+
+
+/**
+ * Subscribe to all changes in ownership and such.
+ */
+BattalionManager.prototype.OnGlobalOwnershipChanged = function(msg)
+{
+	if (this.IsPartOfBattalion(msg.entity))
+		this.Update();
+};
+
+Engine.RegisterSystemComponentType(IID_BattalionManager, "BattalionManager", BattalionManager);
Index: binaries/data/mods/public/simulation/components/GuiInterface.js
===================================================================
--- binaries/data/mods/public/simulation/components/GuiInterface.js
+++ binaries/data/mods/public/simulation/components/GuiInterface.js
@@ -510,6 +510,9 @@
 			"run": cmpUnitMotion.GetWalkSpeed() * cmpUnitMotion.GetRunMultiplier()
 		};
 
+	let cmpBattalionManager = Engine.QueryInterface(SYSTEM_ENTITY, IID_BattalionManager);
+	ret.battalion = cmpBattalionManager.IsPartOfBattalion(ent);
+
 	return ret;
 };
 
@@ -903,6 +906,11 @@
 	return Engine.QueryInterface(SYSTEM_ENTITY, IID_RangeManager).GetNonGaiaEntities();
 };
 
+GuiInterface.prototype.GetBattalions = function(player, data)
+{
+	return Engine.QueryInterface(SYSTEM_ENTITY, IID_BattalionManager).GetBattalions(data.players);
+};
+
 /**
  * Displays the rally points of a given list of entities (carried in cmd.entities).
  *
@@ -1934,6 +1942,7 @@
 	"IsFormationSelected": 1,
 	"GetFormationInfoFromTemplate": 1,
 	"IsStanceSelected": 1,
+	"GetBattalions": 1,
 
 	"UpdateDisplayedPlayerColors": 1,
 	"SetSelectionHighlight": 1,
Index: binaries/data/mods/public/simulation/components/ProductionQueue.js
===================================================================
--- binaries/data/mods/public/simulation/components/ProductionQueue.js
+++ binaries/data/mods/public/simulation/components/ProductionQueue.js
@@ -656,6 +656,13 @@
 			"metadata": metadata,
 		});
 
+	if (false && createdEnts.length > 1)
+	{
+		let cmpBattalions = Engine.QueryInterface(SYSTEM_ENTITY, IID_Battalions)
+		cmpBattalions.FormBattalion(cmpOwnership.GetOwner(), createdEnts);
+		cmpBattalions.Update();
+	}
+
 	return createdEnts.length;
 };
 
Index: binaries/data/mods/public/simulation/components/interfaces/B.js
===================================================================
--- /dev/null
+++ binaries/data/mods/public/simulation/components/interfaces/B.js
@@ -0,0 +1 @@
+Engine.RegisterInterface("BattalionManager");
Index: binaries/data/mods/public/simulation/components/tests/test_B.js
===================================================================
--- /dev/null
+++ binaries/data/mods/public/simulation/components/tests/test_B.js
@@ -0,0 +1,74 @@
+Engine.LoadComponentScript("interfaces/B.js");
+Engine.LoadComponentScript("B.js");
+
+let cmpBattalionManager = ConstructComponent(SYSTEM_ENTITY, "BattalionManager");
+
+let player = 1;
+let group1 = [2, 3, 4, 5];
+let group2 = [6, 7, 8, 9];
+let group3 = [5, 6, 10, 11];
+let allEnts = [2, 3, 4, 5, 6, 7, 8, 9, 10, 11];
+let template = "{civ}/{faction}/{entity}/{rank}";
+let GUItemplate = {
+	"template": template,
+	"player": player
+};
+
+AddMock(SYSTEM_ENTITY, IID_GuiInterface, {
+	"GetEntityState": (owner, entity) => GUItemplate,
+	"GetRenamedEntities": () => []
+});
+
+// No entity is in a battalion yet.
+for (let i of allEnts)
+	TS_ASSERT_EQUALS(cmpBattalionManager.IsPartOfBattalion(i), false);
+TS_ASSERT_UNEVAL_EQUALS(cmpBattalionManager.GetBattalions(), []);
+
+cmpBattalionManager.FormBattalion(player, group1);
+for (let i of group1)
+	TS_ASSERT_EQUALS(cmpBattalionManager.IsPartOfBattalion(i), 1);
+
+cmpBattalionManager.FormBattalion(player, group2);
+for (let i of group2)
+	TS_ASSERT_EQUALS(cmpBattalionManager.IsPartOfBattalion(i), 2);
+
+// No battalions for player 2.
+TS_ASSERT_UNEVAL_EQUALS(cmpBattalionManager.GetBattalions([2]), []);
+
+// Here we form a battalion with parts of another battalion, in-game this should only
+// happen when merging complete battalions, since they are only fully selectable.
+cmpBattalionManager.FormBattalion(player, group3);
+for (let i of group3)
+	TS_ASSERT_EQUALS(cmpBattalionManager.IsPartOfBattalion(i), 3);
+for (let i of group1)
+	if (i == 5)
+		TS_ASSERT_EQUALS(cmpBattalionManager.IsPartOfBattalion(i), 3);
+	else
+		TS_ASSERT_EQUALS(cmpBattalionManager.IsPartOfBattalion(i), 1);
+for (let i of group2)
+	if (i == 6)
+		TS_ASSERT_EQUALS(cmpBattalionManager.IsPartOfBattalion(i), 3);
+	else
+		TS_ASSERT_EQUALS(cmpBattalionManager.IsPartOfBattalion(i), 2);
+
+cmpBattalionManager.DisbandBattalions([1]);
+let result = [
+	{ "id":2, "player": player, "entities": [7, 8, 9], "template": template },
+	{ "id":3, "player": player, "entities": [5, 6, 10, 11], "template": template }
+];
+TS_ASSERT_UNEVAL_EQUALS(cmpBattalionManager.GetBattalions(), result);
+
+// Verify that a removed entity is indeed not part of a battalion anymore.
+cmpBattalionManager.RemoveEntities(2, [8]);
+TS_ASSERT_EQUALS(cmpBattalionManager.IsPartOfBattalion(8), false);
+
+// Verify that once the last entity of a battalion is removed the battalion is disbanded.
+cmpBattalionManager.RemoveEntities(3, [5, 6, 10, 11]);
+cmpBattalionManager.Update();
+result = [{ "id":2, "player": player, "entities": [7, 9], "template": template }];
+TS_ASSERT_UNEVAL_EQUALS(cmpBattalionManager.GetBattalions(), result);
+
+cmpBattalionManager.FormBattalion(player, allEnts);
+cmpBattalionManager.Update();
+result = [{ "id":1, "player": player, "entities": allEnts, "template": template }];
+TS_ASSERT_UNEVAL_EQUALS(cmpBattalionManager.GetBattalions(), result);
Index: binaries/data/mods/public/simulation/components/tests/test_GuiInterface.js
===================================================================
--- binaries/data/mods/public/simulation/components/tests/test_GuiInterface.js
+++ binaries/data/mods/public/simulation/components/tests/test_GuiInterface.js
@@ -34,6 +34,7 @@
 Engine.LoadComponentScript("interfaces/UnitAI.js");
 Engine.LoadComponentScript("interfaces/Upgrade.js");
 Engine.LoadComponentScript("interfaces/BuildingAI.js");
+Engine.LoadComponentScript("interfaces/B.js");
 Engine.LoadComponentScript("GuiInterface.js");
 
 Resources = {
@@ -560,6 +561,10 @@
 	"GetRates": () => ({ "food": 2, "wood": 3, "stone": 5, "metal": 9 })
 });
 
+AddMock(SYSTEM_ENTITY, IID_BattalionManager, {
+	"IsPartOfBattalion": () => false
+});
+
 // Note: property order matters when using TS_ASSERT_UNEVAL_EQUALS,
 //	because uneval preserves property order. So make sure this object
 //	matches the ordering in GuiInterface.
@@ -586,5 +591,6 @@
 	"resourceTrickle": {
 		"interval": 1250,
 		"rates": { "food": 2, "wood": 3, "stone": 5, "metal": 9 }
-	}
+	},
+	"battalion": false
 });
Index: binaries/data/mods/public/simulation/helpers/Commands.js
===================================================================
--- binaries/data/mods/public/simulation/helpers/Commands.js
+++ binaries/data/mods/public/simulation/helpers/Commands.js
@@ -627,6 +627,16 @@
 		}
 	},
 
+	"battalion": function(player, cmd, data)
+	{
+		let cmpBattalionManager = Engine.QueryInterface(SYSTEM_ENTITY, IID_BattalionManager);
+		if (cmd.name == "form")
+			cmpBattalionManager.FormBattalion(player, data.entities);
+		if (cmd.name == "disband")
+			cmpBattalionManager.DisbandBattalions(cmd.battalions)
+		cmpBattalionManager.Update();
+	},
+
 	"lock-gate": function(player, cmd, data)
 	{
 		for (let ent of data.entities)