Elite Army

On one end of the scale of Conservation of Ninjitsu is the Zerg Rush. On the other end is the Elite Army.

Instead of sending endless waves of disposable mooks at the enemy, this army relies on a small amount of very deadly soldiers to win the battle.

They're up against a Redshirt Army that outnumbers them five to one, but the Redshirt Army doesn't stand a chance. Maybe they have superior training. Maybe they have better equipment. Maybe they're all Super Soldiers. Maybe its a combination of the three. The point is, a soldier in this army is worth five of the enemy's.

Usually it will be said that one single soldier in this army is worth X soldiers in any other army.

This usually means each individual will be much more valuable so No One Gets Left Behind.

Basically, while the Zerg Rush is Quantity Over Quality, the Elite Army is Quality Over Quantity. When it's just one soldier doing all this alone, it's a One-Man Army.

When they are the bad guys, they are Elite Mooks.

This is usually a Badass Army, but it specifically refers to when the army is smaller than most other armies.

Examples of Elite Army include:

Anime & Manga

Berserk has the group of mercenaries known as the Band Of The Hawk, featuring Guts and Griffith and under 8 others, who dominated all in their path, and overcame almost any challenge. Well, almost any challenge.
When applied to high school delinquents, one example is "Kitano's Hekikuu Army" in Angel Densetsu. They have only four main fighters but won a fight against a far more numerous enemy force in the last chapter.
In Ikki Tousen this pretty much describes Seitou's combat force. Other forces such as Kyoushou appears to have plenty of Red Shirts sprinkled with a few Elite Mooks but Seitou generally has to rely on Kan'u or Chou'un to repulse any concerted assault.

Comic Books

300 Spartans against the entire Persian Empire. The Persians eventually kill the Spartans, but it takes a hell of a lot of soldiers.

Literature

In the later books of the Ender's Shadow series, Bean commands a special unit of 200 Thai soldiers, who execute a number of critical missions, then commands the small army of the newly-created Free People of Earth under the Hegemon.
In 1632, three thousand soldiers of Tilly's mercenary army, armed with seventeenth century weapons, comes up against the four hundred member's of Grantville's "army" (armed with modern weaponry and modern vehicles) like a log hits a rotary saw. The end result is nearly twelve hundred mercenary prisoners, nearly eighteen hundred dead mercenaries, and four hundred victorious Americans.
The Mobile Infantry of the original Starship Troopers are very elite and use Powered Armor.
The Unsullied of Astapor, as featured in A Song of Ice and Fire. They are called the finest foot in the world, because they have discipline and intense training. However, they're not all that good at non- or para-military matters.
The Black Forces of Hungary in Count and Countess.

Tabletop Games

It takes just a few hundred Space Marines to conquer an entire planet in the Warhammer 40,000 galaxy.
- And amongst Space Marines which follow the Codex Astartes, the First Company (Veterans) and Honor Guard are considered elite compared to them.
- The Grey Knights are considered to be the elite of the space marines, with their previous codex lampshading how hard it is to actually play said army without using the allies rule due to being constantly outnumbered.
In Dungeons & Dragons, the Devils are this to the Demons. They field much smaller number in the Blood War, but the soldiers are well-regimented and trained, and able to fight the practically infinite number of Demons to a stalemate.
The Clans from BattleTech number less than the Great Houses of the Inner Sphere, but thanks to having a culture completely devoted to military prowess, they nearly ended up conquering the entire Inner Sphere.

Theater

In the battle of Agincourt as shown in Henry V 12,000 English troops are up against 60,000 French. After the battle there are 10,000 French dead and 25 English.
- Ironically, however, the French army was very elite and a formidable fighting force, but too gung ho for its own good.

Video Games

The Protoss units in StarCraft are expensive, but powerful.
- Part of Starcraft's legacy is that most military strategy games have the three races: A race that uses the Zerg Rush (which StarCraft also named), a race that's the Jack of All Stats and a race that uses this trope.
The US Army in Command & Conquer: Generals leans this way.
The Spartans of Halo. Subverted in that they're part of a larger force.
Fire Emblem uses this trope in conjunction with the Arbitrary Headcount Limit, giving you ten to fifteen units to take down the enemy army. One of the most notable examples is in Blazing Sword, where you must defeat an enemy army of roughly sixty troops (with reinforcements spawning in every few turns) with about fifteen units.
The Allied Peacekeeper Division in Red Alert 3 Paradox is an international Elite Army, supplemented by the more conventional army in the Allied Reservists.
Kanbei's Yellow Comet, in Advance Wars. His troops are more expansive and more powerful, which means that even though you'll see less of them during a battle, you may have more trouble getting rid of them than with other, more numerous, troops.

Real Life

The Battle of Thermopylae, although the graphic novel and film exaggerates this a bit.
During the Battle of Mogadishu, later depicted in the novel and film Black Hawk Down, a small group of 160 US Rangers and Delta Force operators supported by some Malaysian and Pakistani armoured vehicles fended off somewhere from two to four thousand Somali militiamen.
- Somewhat downplayed in practice, as is often the case in peacekeeping missions in that part of the world. When your opposition knows about as much about basic infantry tactics as you can pick up from playing Call of Duty, any reasonably well-trained and professional unit of regular infantry is going to look like this trope by comparison.
During the 15th and 16th centuries, small armies of Spanish Conquistadors managed to conquer the entire Incan and Aztec civilizations, due to a combination of disease, Enemy Civil War and liberal amounts of This Is My Boomstick.
In an insect world example, compare the number of Japanese hornets to European honeybees and who wins.
- The Hornets, although Japanese bees use Zerg Rush tactics to make bee balls and cook the head sensitive hornets alive.
Being able to win through against larger numbers of enemy fighters is half the point of special forces. The other is specialising in operations too difficult for normal troops to handle.