North Korea
Type 59: The Type 59 is a Chinese variant of the Soviet T-54A and North Korea is estimated to have 1000 in service (a total of 2000 Type 59s and T-55s). As the name suggests, the Type 59 came about before hippies were even a thing and is typical of North Korean arms: very old and probably not in very good condition. The main gun is a manually loaded 100mm rifled gun with a typical combat load of 34 rounds, and it also includes two 7.62x54mm machine guns (one coaxial to the main gun and one for the driver, allowing it to fire at infantry who make the mistake of moving directly in front of the hull) and a 12.7x108mm heavy machine gun on top of the turret for the commander's hatch. Later models feature vertical gun stabilization and an infrared searchlight for night vision, but it's unclear if North Korean tanks will be fitted with one. The tank has a maximum range on roads of 600 km, or 430 km using only the internal tanks, but it's doubtful that DPRK tanks will have a full fuel load and the range will be much lower should they need to travel through the mountains.
One major disadvantage is the poor ammunition storage in the turret, which makes it very likely that any impacts there from another tank or an anti-tank rocket will basically send the turret (and its occupants, or at least part of them) flying into the air. As far as I know the tanks have not seen combat against modern MBTs like the Abrams, but ideas can be gleaned from how other old Soviet tanks fared during operations in Iraq: not very good.
T-62: The standard Soviet tank through most of the 60s and 70s. It's mostly a modification of the T-55, and thus maintains many similarities to the above Type 59. It has a two-axis stabilizer on its 115mm smoothbore gun, the world's first smoothbore tank gun, in fact, and has accuracy comparable to the M60 Patton (at least at a standstill against a stationary target) that it would have faced should the USSR and US have come to blows during the Cold War. Like the M1 Abrams used by the United States, there's no autloader and every round must be loaded by hand (though empty casings are automatically ejected), giving a practical rate of fire of 4 rounds per minute that decreases when the vehicle is moving. The tank can also inject vaporized diesel fuel into the exhaust system to create a smokescreen, though this may be a waste of fuel for the starved North Korean logistics. It maintains the 7.62mm coaxial machine gun and 12.7mm heavy machine gun on top of the turret from the Type 59, but lacks a machine gun for the driver.
It shares many limitations of Soviet tanks of this time: a cramped crew compartment (though this is less of a difficulty for the small North Koreans), limited ability to depress the main gun (which is a big difficulty in the mountains, since the tank will need to be parked on a steeper incline to fire downward in an ambush), and there's even been many incidents where crew members were injured by ejecting shell casings ricocheting into the crew compartment. The power traverse for the turret is disabled during shell ejection and loading, which greatly slows aiming speed until the gun can be reloaded, and the loader must partially expose himself and abandon his obviously vital duty to fire the 12.7mm. For these reasons, the T-62 saw most of its success with foreign sales. And there's the obvious problems with the steel armor being easily penetrated by a modern MBT's main gun.
T-55: At 1600 tanks, this is thought to be the most numerous model in the North Korean Army. Back to the 100mm rifled gun (similar to the one on the Type 59 but of actual Soviet design), with the single 7.62mm coaxial gun and optionally a 12.7mm heavy machine gun like the T-62. The T-55 is an upgrade to the T-54, carrying 45 shells for the main gun (with 18 carried in "wet containers" in the hull fuel tanks; enjoy!) and fitted with a night vision device for the gunner. The T-55 was one of the first "main battle tanks", eliminating the divisions in weight and strength classes of tanks in favor of a single general purpose design. As with most Soviet technology, it's simple and robust and designed for mass production and mass fielding. They have good mobility on soft ground due to the wide track base and relatively light weight (which also lets them more easily cross bridges or be transported by train and truck). They also often come with snorkels to allow for limited water crossing and a good cold weather startup system, a necessity in the Russian conditions, and a low silhouette (well suited for small North Korean tankers) that makes them easier to hide.
Of course, the drawbacks are numerous: the armor and gun simply don't compare to modern MBTs, to the point where its armor was obsolete within 20 years of production and the tank needs constant upgrades to keep it relevant as an individual force. They were designed for traditional warfare, with tanks fighting in formation on open fields of battle, and as such their side and rear armor is very thin and can easily be penetrated by 40-year-old anti-tank rockets like the M72 LAW. They've also got issues with unshielded ammo storage, and like the Type 59 it's badly at risk of a catastrophic "cookoff" if the ammo is hit.
PT-76: A Soviet amphibious tank, which isn't something you see on the modern battlefield. The PT-76 has a wide, boatlike hull that makes its silhouette obvious to anyone who spots it. It only carries two weapons: a 76.2mm rifled gun and a 7.62mm coaxial machine gun. The PT-76 is designed along the "light tank" line of thinking, with the Soviets intending to use them for reconnaissance. One big issue with the tank is that the commander also has to act as the gunner and radio operator, which limits operational efficiency due to the guy who directs the tank simply being too busy doing the jobs of one or two other people as he tries to consider the situation and direct his driver. Like many Soviet tanks, it's intentionally simple and rugged and works well in cold weather. It also includes an emergency hatch under the driver's seat in case sudden evacuation is needed out the belly of the tank. The maximum water speed is 10.2 km/h and it has a range of about 100 km. The driver's the only one with a night vision device and it has no special fire or NBC protection, which makes it pretty vulnerable. It's believed that 450 are in the North Korean arsenal, where they would likely be used (at least initially) for scouting.
Because of the buoyant design, it's disproportionately large for its weight and consequently has little armor. The tank is likely highly vulnerable to infantry portable anti-tank weapons, to say nothing of what a modern tank gun would do to it. And there's the obvious issue of it sinking if damaged while in the water, which could easily doom the crew to a slow and painful death.
PT-85: An independent amphibious design, this one based on an APC chassis. Very little information is known, but it is known to have an 80mm main gun and an anti-tank guided missile launcher, with a speed of 10 km/h in water and 60 km/h on roads.
Ch'ŏnma-ho: The "Sky Horse" or "Pegasus" is a secretive indigenous tank design, with at least five different operational variations (the earliest based on the T-62) and constant upgrades throughout its service life. At least 1000 are believed to have been produced. According to the North Korean strategy, the Chonma-ho would act as the vanguard to break through the DMZ into South Korea. At least 90% of the components appear to be indigenously produced, but evidence has suggested that entire engines and engine components from Slovakia, of all places. There's also been purchases of ceramics, apparently to try and upgrade the armor similarly to the Chobham armor used on the M1 Abrams, and fire suppression capabilities. It's also been seen with what looks like explosive reactive armor, which further protects it from anti-tank rounds or rockets. It has a 115mm or 125mm smoothbore gun, a 7.62mm coaxial machine gun, and a KPV 14.5mm heavy machine gun on top.
This new design is the closest the North Koreans have come to reaching modern MBT design, which would make it a formidable foe in tank warfare. That said, there's no guarantee that it's a direct competitor to the M1 Abrams, and the obvious issue of logistics makes it harder for the North Koreans to keep their toys fueled and repaired.
P'okp'ung-ho: Another indigenous design, incorporating technology from Soviet tanks ranging from the T-62 to the modern T-90. The creation was apparently inspired by the American actions in Desert Storm, where the M1 Abrams blew T-72s to shreds in open warfare. Armament is almost certainly a 115mm or 125mm smoothbore gun, as well as a 7.62mm coaxial gun and a KPV like the Chonma-ho. The tank follows North Korean tactics of aggressiveness and quick speed, and the tank has correspondingly high acceleration and speed (though only suitable for the mountains, where a big 1200 horsepower engine would go to waste). The fire control system appears to be stolen from the British Chieftain of the 60s and 70s, and it appears to have full night fighting capabilities. It's believed to be very dangerous at short and medium ranges due to the equipment (including a laser rangefinder), but will do poorly at long range at night.
South Korea
K1: The current main battle tank of South Korea and based on early M1 Abrams designs. The K1 has a 105mm rifled gun, while the K1A1 upgrades similarly to the M1A1 Abrams with a 125mm smoothbore. Machine guns include a locally produced M2 Browning in .50 BMG on top of the turret with an M60 in 7.62x51mm NATO next to it, as well as another M60 on the coaxial mount. Only about 1500 are in service, but each one is a very modern vehicle with a powerful gun and heavy armor, as well as various computerized systems and useful equipment. Technology includes Chobham armor like that used on the Abrams (a metal/ceramic composite that makes even modern MBTs have trouble penetrating into the crew compartment) and an automated fire extinguisher. However, the tank lacks seals against NBC attacks (which would not be unprecedented for use by North Korea) and the crew will be forced to rapidly don NBC gear in the vehicle or retreat in case of an attack.
K2 Black Panther: The K2 is the newest MBT design and is set to be what replaces all of the old M48 Pattons and complement the K1. After the AMX-56, this is the most expensive tank in the world at $8.5 million per unit. The prototype wields a 120mm smoothbore gun with 40 rounds available (including a brand new tungsten penetrator round that apparently sharpens itself on impact and a top-attack round that shoots into the air and comes down on the thin top armor of the turret), an M2 Browning on a pintle mount on the turret, and a coaxial 7.62x51mm machine gun. Other features include a radar and radar jammer, soft-kill system for defeating incoming missiles, and laser detectors that immediately fire infrared smoke grenades in the direction of lasers contacting the armor to defend against being "painted" by a rangefinder. Mass production and entry into service has been delayed until March of 2014 due to issues with the transmission and engine, but there's a possibility that if pressed, South Korea will bring them into use to supplement their current tank corps (or use the war as a chance for immediate field testing).
M48 Patton: This is an old tank, entering service in 1953, but remains in the inventory of South Korea until newer tanks can be provided. The Patton is closer to North Korea's T-55s and Type 59s, which makes battles involving them a much more precarious prospect for the South Korean forces. The Patton is armed with a 90mm or 105mm main gun, an M2 Browning .50 caliber on the top pintle mount, and an M73 7.62x51mm machine gun or M60 machine gun on the coaxial mount. The South Korean tanks have received some modifications, like an indigenous fire control system and a diesel engine, but the 880 tanks in service are still decidedly old.
T-80: As the name suggests, this is a Soviet design. South Korea acquired 35 of them recently, 33 of the U variant and 2 of the UK. It was the first tank to be fitted with a gas turbine engine rather than a plain gasoline or diesel internal combustion engine, and has been in service in Russia and various other nations since 1976. It carries the 125mm smoothbore gun of the T-72, fitted with an autoloader that holds 28 rounds (of 45 total) and gives it a rate of fire of about one shot every 7.1 or 19.5 seconds (depending on the exact position of the autoloader's mechanism). It has even lower ground pressure than the T-64, making for easier crossing of bridges and soft ground. It still has an issue with catastrophic explosions in case a shell breaches the ammo compartment, which means that a lucky shot can completely kill the tank AND its crew.
United States
M1 Abrams: The first tank in the world to be fitted with Chobham armor and the baseline for modern MBTs. The Abrams has gone through many variations since it first came into service in 1980, and the current standard is the M1A2. Over 8000 units are currently in service, a greater number than all North Korean tanks combined. The M1A2 is fitted with a 120mm smoothbore gun with 42 rounds, an M2 Browning and M240 in 7.62x51mm on pintle mounts on top of the turret, and a coaxial M240. The Abrams is sometimes considered unusual for having a loader as part of the crew instead of fitting an autoloader, but this has its own advantages: the loader can often get faster speeds than an autoloader, and he can also pull other duties (like helping with repairs, guard duty, or taking over the job of an injured or killed crewmember).
The Abrams is notoriously tough, with even other Abrams tanks having trouble killing them with multiple point blank shots (and its gun is also known for being an extremely good penetrator). However, the tank is not invulnerable; even heavy machine gun rounds have disabled the vehicle or components with good shots, and they're vulnerable to IEDs or close range shots to spots like the treads from RPGs. The mountainous terrain and many urban areas (such as villages and major cities like Pyongyang) would present many opportunities for such ambushes.
The North Korean tank complement, except for a pair of secretive indigenous designs that begin to reach toward modern capabilities, are just as old as the rest of their equipment. Similar models have recently faced action against modern American vehicles in the Middle East to disastrous results, and the M1 Abrams is overwhelmingly superior to all known models (and likely superior to their two new ones) while also being more numerous than all combined models of North Korean tank. However, the advantages of the Gulf War and the recent war in Iraq (wide open terrain with long ranges and direct tank vs. tank combat) are lost in North Korea, where the mountains and valleys both slow the Allied advance and make ambushes much easier to perform, as well as making close air support more difficult to properly apply. South Korea has tanks of a similar capability to the American Abrams, but they also have large numbers of Cold War vehicles that may need to be brought out if necessary and will be more comparable to North Korean vehicles.
One major disadvantage to the North Koreans is the large number of tank models in use. While many of them are from similar stock, they're not identical. The more vehicle types you have to maintain, the harder it is to produce enough spare parts and ammunition for all of them. South Korea has this issue to a smaller degree, while the United States exclusively uses the M1 Abrams and only needs to produce ammo and parts for one model.
