Taiwan's military is training for urban warfare against Chinese troops. Here's the kind of fight they're facing.

• Russia's attack on Ukraine has raised concerns about China attacking Taiwan.
• China has military superiority by most measures, but Taiwan has the advantage of defense.

China has for decades vowed to absorb Taiwan, a self-governing island that Beijing regards as a breakaway province.

Beijing has said it would pursue unification through force if necessary, and Taiwan's military has been increasing its budget and intensifying its training in order to improve its ability to fight off such an assault.

China has been modernizing its military as well, adding scores of fighter jets and dozens of warships. If it were to invade Taiwan, however, it would likely face a scenario where high-end weapons would be of little advantage: urban warfare.

'An equalizer'

Taiwan is home to about 23 million people, most of whom live in several major cities where a war for the island would be won. China's military has superiority on pretty much every level, but Taiwan has the advantage of defense, which its military is betting on.

"The Chinese communist troops' battle plans will be invading and landing firstly from coastal towns. Then the fighting will progress into more populated residential and commercial areas and lastly push into mountainous villages. Any future battle to protect Taiwan will be an urban warfare," Lt. Col. Kiwi Yang, a military instructor at the Taiwan Army Infantry School, told news agency AFP.

Urban warfare is one of the most challenging military operations. City streets and alleys are easy to barricade and inhibit maneuver warfare. To capture a city, a military has to sacrifice its agility for brute strength.

The Russian invasion of Ukraine shows how difficult and costly urban warfare is. For weeks, Russian forces has been trying to capture the southern Ukrainian port city of Mariupol, but they have been thwarted by determined defenders with modern anti-tank and anti-aircraft weapons.

China's military is surely taking notes from Russia's operations in Ukraine to inform its own plans for a potential invasion of Taiwan, but fighting in urban environments will remain costly for even the most technologically advanced military.

"Much like water, urban warfare is an equalizer. You put a bunch of city blocks in the equation and all of a sudden you and the opposition are on a more even scale. You see any technological advantage you have devalue[d]," a US Army Special Forces officer, who is on active-duty and requested anonymity, told Insider.

The inherent advantages of defense are increased in an urban environment, the officer said, pointing to events in Mariupol as an example.

The Ukrainians "have been holed up against the Russians for weeks now. The Russians have the complete sea, air, and long-range fires advantage, though they lack our precision-strike capabilities," which could explain why they resort to indiscriminate shelling, the officer told Insider. "Despite their advantages, they are still struggling to take the city."

The defenders have more freedom of movement within the city. They can engage the attackers at times and places of their choosing and inflict heavy casualties.

Success in such an environment requires mastery of small-unit tactics and close-quarters combat, and regular infantry typically isn't as proficient in those skills as top-tier special-operations forces. "There would be no hostages to rescue in a building, and a grenade could solve a lot of problems in such scenarios," the Special Forces officer said.

Taiwanese forces could likely "hold out for a good amount of time," the officer added. "They have a competent military with many advanced weapon systems. They are well-prepared and they know where the enemy will be coming from."

Should China invade Taiwan, it would have to make sure that it can defeat the defenders in a few days or that it can blockade Taiwan to prevent outside intervention for an extended period.

"Yes, the Chinese might win at the end of the day because of their sheer numbers, but it won't be easy and it will cost them a lot. What we're seeing unfolding in Ukraine right now is the best deterrence Taiwan could ask for," the officer told Insider.

Stavros Atlamazoglou is a defense journalist specializing in special operations, a Hellenic Army veteran (national service with the 575th Marine Battalion and Army HQ), and a Johns Hopkins University graduate.