Kalran: Tales of the four nations/Tier

In Kalran: Tales of the four nations, advance infantry, vehicles, upgrades, and so on are locked behind a tier system, requiring the commander to invest resources to unlock their stronger armaments, though how is different per factions. Every faction has only 4 tiers and 3 tech levels. Each faction's headquarters initially set their alert status to Tier 1, not Tier 0.

Tiering up
There are a total of three tiers each factions have and a unique method each of them have to access advanced units, structures, or upgrades, depending on their type:

Earthborn (Dwarves, Fenrir, Xiagui, Goliath), ADF, and Ouroboros
The Earthborn build their structures directly from their bases, similar to command and conquer, by building them in storage before instantly deploying them on the field, so long as they're in a command radius, with their worker units mainly being more combat support. While this does make their base building the most secure it also makes theirs the slowest since they can only make one building per base, compared to the Waterborn using builder units, the Fireborn not needing to build, and the Windborn sending out units that instantly deploys into structures, all three of which doesn't rely on needing a command field.

The commander of these factions are rather unique in that they have a total of three tech trees, each with their own three tiers, and are expected to upgrade down all the trees in time, but prioritization is important. As in order to tech up they must first tech up their base, only when the base tier is equal or above the tech building in their zone will they be able to upgrade said buildings.

Waterborn (Humans), Byzalem, and Asura
The Waterborn builds their structures using worker units, and can shorten the build time up to ten workers can focus on a structure. While this is fast and allows them to rapidly build up it is also vulnerable to having its workers killed, since they become frail while building, the structure can be destroyed before it can properly be finished, and they require power to function, if they lose too much generator their production slows and their defense shuts down.

The commander techs up by upgrading at least one hq to the next tier, with more specific units/protocols be unlocked by smaller and cheaper tech buildings. But they only need one base at a higher tier for their facilities to access their advance units/upgrades. While slower then the windborn and fireborn its faster then the earthborn and allows the commander to expand easily.

Fireborn (Orcs, Rokhari, Salamander, Mukasura), Guilds, and Horde
Unlike the other factions the Fireborns hq, production buildings, and superweapons are completely mobile, with their worker units only tasked with building defenses. While this allows them to push forward and replenish losses rapidly, since their building can be close to the front lines, they suffer from little to no static defenses, meaning that they must attack to counter an enemies push.

Compared to the other they rank up by spending protocol points, upon which all the units, upgrades, and protocols from that tier are instantly unlocked and ready to spend/research. Encouraging the commander to be more aggressive to gain experience and tech up faster, while making more defensive commanders lag behind.

Windborn (Elves, Navaheim, Nekomata, Faunus), Tenko, and Reclaimers
Compared to the other factions the Windborn builds by either using cheap building units that expands themselves to build, like the nanocores from red alert 3 or drone from starcraft, or have the worker unit only needing to lay down the initial building and letting it complete itself, like the acolyte from warcraft or the probe from starcraft, This, combined with not needing to build in a command radius or needing power, means they expand the fastest of the factions, though individually their structures and defenses are weaker.

They also have the faster rank up by only need to build their factions tech buildings to rank up, after which all of their production techs up. While this allows the commander to tech up the fastest their late game units, while cheaper compared to equivalents, are rather lacking in comparison, and their buildings and tech tree are comparatively linear, meaning its rather easy to see what tier their in.

Tier 0
The first tier, usually known as Tier 0 and sometimes known as "Basic", consists of the basic units that can be constructed from production structures without the need of any other structures.

Some examples of these units are initial infantry (reconnaissance, basic, support and anti-armor), basic vehicles (reconnaissance, anti-infantry, armored car, anti-armor, infantry transport, anti-air, IFVs, light tanks, and possibly MBTs), basic aircraft (light and transport VTOL craft/helicopters/rotorcraft, and fighters), and basic vessels (patrol boats, frigates, destroyers, and corvettes).

Tier 1
The second tier, usually known as Tier 1 or the first alert status level and sometimes known as "Standard", is started by the following list below. This tier grants access to advance infantry squads, vehicles, mainly tanks, and aircraft as well as faction/commander-exclusive units.

Tier 2
The third tier, usually known as Tier 2 or the second alert status level and sometimes known as "Intermediate", is unlocked by primarily economical buildings. This tier unlocks heavier vehicles, mid-level aircraft, specialized infantry, hero units, and secondary economy structures, as well as the next tier of structures.

Tier 3
The fourth tier, usually known as Tier 3 or the third alert status level and sometimes known as "Advanced", is unlocked by Tier 2 tech building. This tier consists of heavy/advanced artillery, heavy/advanced anti-air, heavy units meant to break any stalemates, superweapons, all other locked units, and most of all the commanders Epic.

Minor exceptions
There are some exception to this rule though. Below are factions whose tier differs:

Delteroa Self-Defense Forces: They are one of the factions to have no tier requirements for their units. Once a production structure is place all of its associated units are unlocked instantly, allowing them to both expand quickly and deploy more specialized units far quicker then the rest. But they are severely expensive with an initially bad price to power ratio, especially when compared to similarly expensive factions like the UCA, a terrible economy, with both the worst harvester and economy building, a heavy reliant on their global upgrades to compete, and only able to research two out of six per tier level, and said specialist unit will completely lose to the other factions means that they must rely on guerrilla tactics and stacking the odds against their foes to win.

Reclaimers: Similar to the DSDF the Reclaimers have no tier requirements for their clone units. Once their Control Core is place all of their clone units are unlocked instantly, with the tier upgrades instead increasing the number of clones teleported per charge and advance chosen units, and unlike the other they have no build time, once ordered the unit/structure is instantly teleported to the field, combined with the clones ridiculously cheap price means that they can literally build an army in seconds. But you get what they payed for, as in all of their units WILL lose when facing their counterparts unless they outnumber them ten to one. And they are the only faction that has no way to upgrade their units, especially if the commander is Bahlgram, meaning that by late game the only advantage they have is their ability to spam more units, powerful protocols, and can instantly replace losses to overwhelm their enemies. And they are the only faction to have a population cap in Stabilisers, though the cap itself has no limit, meaning that building said army requires a few Stabilisers.

United Columbia Alliance Armed Forces: The UCA prototypes division tree is rather unique in that its structures, the Prototypes workshop and the Aeronautics complex, have all of its associated units instantly unlocked, with its tier upgrades mainly unlocking more advance upgrades and powerful protocols. But unlike the other two these units are severely expensive, meaning they are small and the loss of one is bad, meaning the commmander needs to be careful when using them and to have some cheaper units protecting them.