A Guide to the World's Militaries, Suggested reading before fighting

[Pakistan (CSJ)]

MECHANIZED FORCES


The complement to armor, infantry are necessary to protect tanks in restricted terrain, hold ground, and assault some types of fortified positions. Mechanized forces use IFVs to ensure that mobility and survivability of infantry forces are as close to armored units as possible. Both are rarely found without the other. As with armored, these are often offensive formations and therefore also have highly variable nature.
While I use the term IFV here, as that's most common, many larger and/or less well equipped militaries use cheaper APCs, which often have larger infantry squads. Also note that command IFVs/APCs rarely have full squads, but rather a command staff of 2-4 with additional communications gear.


SECTION:
The smallest administrative unit for infantry, consists of 3-4 soldiers and their equipment. Always homogenous for obvious reasons.
-ALL (vehicle): 1 IFV plus crew of 2-3
-ALL (infantrymen): 3-4 soldiers

SQUAD:
The smallest maneuver unit for infantry. May operate alone as a patrol, or more likely as part of platoon-level operations. Always homogenous. Variance on size is entirely based on doctrine or carrying capacity of the APC or IFV used. APC-based units typically have 1-2 more infantry sections due to higher carrying capacity, and to balance lack of firepower on the vehicle.
-ALL: 1 vehicle section & 2-4 infantry sections (1 IFV & 6-12 infantry)
-Older Soviet Airborne: 1 vehicle section & 1 infantry secton (1 IFV & 4 infantry)

PLATOON
The most common maneuver unit for small-scale operations. A platoon is generally considered the minimum for holding a piece of land, as it can patrol with 1 squad while the main force can attack or defend.
-US/Europe: 4 squads (4 IFV & 24-48 infantry)
-Russia/China/UK: 3 squads (3 IFV & 18-36 infantry)

COMPANY
The most common maneuver unit when operating with armor. Sometimes trades platoons with tank companies, in which case both are called teams in US military. May have additional support units, such as mortars or ATGM teams, in other APCs or trucks.
-US: 3 platoons, 2 command IFV (14 IFV, 72-144 infantry)
-UK: 4 platoons, 2 command IFV (14 IFV, 72-144 infantry)
-Europe: 3 platoons, 1 command IFV (13 IFV, 72-144 infantry)
-Russia/China: 3 platoons, 1 command IFV (10 IFV, 54-108 infantry)

BATTALION
Similar in role to an armored battalion, but with greater emphasis on defense and holding territory. When trading companies with armored battalions, both are known as task forces. Usually have similar levels of support compared to armored battalions, including mortar battery.
-US: 3 (formerly 4) companies, 2 command IFVs (44 IFVs & 216-432 infantry, or 58 & 288-576)
-UK: 3 companies, 1 command IFV, 11 more in ATGM company, (54 IFVs & 282-498 infantry)
-Europe: 4 companies, 3 command IFV (55 IFV, 288-576 infantry)
-Russia: 3 companies, 1 command IFV (31 IFV, 162-324 infantry)
-China: 4 companies, 0-1 command IFV (40-41 IFV, 216-432 infantry)

BRIGADE
Extremely similar to a tank brigade, in many cases with the only difference being one tank battalion replaced with a second of mechanized infantry. They will have the same support as armored brigades, and also may be independent or divisional.
-US: 1 tank & 2 mechanized battalions (44 tanks & 88 IFVs, or 58 tanks & 116 IFVs)
-UK (independent): 1 tank & 2-3 mechanized battalions (44-45 or 58-59 tanks, 108 or 162 IFVs)
-UK (divisional): as above, or 3 mechanized battalions (162 IFVs)
-Europe: 1 tank & 2 or 3 mechanized battalions (53-55 tanks, 110 or 165 IFVs)
-Russia (independent): 1 tank & 3 mechanized battalions (31 or 41 tanks, 93 IFVs)
-Russia (divisional): 1 tank & 2 or 3 mechanized battalions (31 or 41 tanks, 62 or 93 IFVs)
-China (divisional): 0-1 tank & 3 mechanized battalions (0 or 31-33 tanks, 120-123 IFVs)
-China (independent): 1 tank & 3-4 mechanized battalion (31-33 tanks, 120-123 or 160-164 IFVs)
NOTE: While rare in these nations, some countries may employ independant mechanized brigades with 2 tank and 2 infantry battalions.

DIVISION
This is where the line blurs completely. The difference between an armored and a mechanized division in the US and UK is usually a grand total of 1 battalion, with all else being identical. Support levels are the same as for armor.
-US: 1 tank & 2 mechanized brigades (176 or 232 tanks & 220 or 290 IFVs)
-UK (homogenous brigades): 1 tank & 2 mechanized brigades (132-135 or 174-177 tanks, 324 IFVs)
-UK (mixed brigades): 0-1 tank & 2-3 mechanized brigades (as above, OR 176-180 or 232-236 tanks, 270 IFVs)
-Russia (4 brigades): 1 tank & 3 mechanized brigade (155 or 186 tanks, 217 or 330 IFVs)
-Russia (3 brigades): 1 tank & 2 mechanized brigade (124 or 155 tanks, 155 or 217 IFVs)
-China: 0-1 tank & 3 mechanized brigade (0-200 tanks, 360-369 IFVs)

[Pakistan (CSJ)]

MOTORIZED FORCES

A variation on mechanized forces, but with cheaper and less expensive transportation. For most armies, this means trucks instead of APCs or IFVs, though heavily mechanized militaries may use the term for APC-equipped units. Unlike mechanized formations, these are almost always homogenous.


SECTION:
The smallest administrative unit for infantry, consists of 3-4 soldiers and their equipment. Always homogenous for obvious reasons.
-ALL (vehicle): 1 APC or truck, plus crew of 1-2
-ALL (infantrymen): 3-4 soldiers

SQUAD:
The smallest maneuver unit for infantry. May operate alone as a patrol, or more likely as part of platoon-level operations. Always homogenous. Variance on size is generally based on the vehicle used for transport.
-ALL: 1 vehicle section & 3-4 infantry sections (1 truck & 9-12 infantry)

PLATOON
The most common maneuver unit for small-scale operations. A platoon is generally considered the minimum for holding a piece of land, as it can patrol with 1 squad while the main force can attack or defend.
-US/Europe: 4 squads (4 trucks & 36-48 infantry)
-Russia/China/UK: 3 squads (3 trucks & 24-36 infantry)

COMPANY
The most common maneuver unit when operating with armor. Sometimes trades platoons with tank companies, in which case both are called teams in US military. Usually has an additional support platoon with mortars, ATGMs, SAMs, and/or machine guns (not counted here).
-US/Europe: 3 platoons (12+ trucks, 108-144+ infantry)
-UK: 4 platoons (12+ trucks, 108-144+ infantry)
-Russia/China: 3 platoons (9+ trucks, 72-108 infantry)

BATTALION
The main formation for infantry units. Always includes a heavy weapons company with machine guns and antitank weapons, and usually medium or heavy mortars (not included in below figures).
-US/Europe: 4 companies (48+ trucks & 432-576+ infantry)
-UK: 3 companies (36+ trucks, 324-432+ infantry)
-Russia: 3 companies (27+ trucks, 216-324 infantry)
-China: 4 companies (36+ trucks, 324-432 infantry)

BRIGADE
Unlike mechanized forces, these are almost always homogenous, and are rarely seen outside of divisions. They may include a tank company as part of the cavalry/reconnaissance force, but usually do not have any armor. They still have the other usual support, including artillery and air defense.
-US/Europe: 3 battalions (144+ trucks, 1296-1728+ infantry)
-UK: 3 battalions (108+ trucks, 972-1296+ infantry)
-Russia: 3 battalions (81+ trucks, 648-972 infantry)
-China: 3-4 battalions (108-144+ trucks, 972-1728 infantry)

DIVISION
Usually reserve or defensive formations, motarized divisions may have an armored brigade or independant armored battalion attached, but usually do not. Otherwise, they have much the same support as mechanized forces, just with less expensive alternatives like towed or truck-mounted artillery instead of traditional self-propelled weapons.
-US/Europe: 3 brigades (432+ trucks, 3888-5184+ infantry)
-UK: 3 brigades (324+ truck, 2916-3888+ infantry)
-Russia: 3 brigades (243+ trucks, 1944-2916+ infantry)
-China: 3 brigades (324-576+ trucks, 2916-5184+ infantry)