The World’s Largest Militaries, Ranked by Active Troops

The US military may lead the world in budget size and in the ambitions of its warfare technology, but there is one measure by which it is outsized by other nations.

Using data from the International Institute for Strategic Studies’ 2026 Military Balance report, Business Insider ranked the top 25 countries by the size of their active armed forces during 2025 and listed their defense budgets that same year.

Active-duty force size is a tally of a country’s uniformed troops: airmen, soldiers, sailors, special operators, and Marines.

Armies, in particular, depend on size to gain and occupy ground during armed conflicts.

Militaries can also be a tool of domestic repression. North Korea, for example, is one of the world’s most repressive states, led by a dictator who has repeatedly threatened neighboring South Korea — and it also has one of the world’s largest militaries.

The number of active-duty military personnel is far from the only factor that matters when comparing military power between countries, but it reflects latent power.

“Numbers have value, but there’s a lot more to military capability,” Mark Cancian, a senior advisor at the Center for Strategic and International Studies, a Washington, DC-based foreign policy and national security think tank, told Business Insider.

IISS, a London-headquartered think tank, counts active armed forces, reservists, and paramilitaries as separate categories in its analysis, showing a fuller picture of each nation’s manpower.

Some countries have significantly more reservists than others — Vietnam has the largest number in the world, estimated at 5 million — but the quality and longevity of their expertise can vary between systems.

“When you look at some countries’ reserve numbers, you’re often looking at people who haven’t trained in 10 or 20 years,” Cancian said. “It gives you a big number, but their military value is questionable.”

Even when accounting for all of a military’s manpower, personnel is only one of the factors that can qualify a nation’s military strength, which also includes equipment and readiness.

There’s also the role of technologies in global warfare, the size and sophistication of air forces and naval fleets, amphibious capabilities for landing assault forces, command-and-control systems, and nuclear forces, all of which shape military power.

Still, comparing global manpower offers insight into how countries prioritize military power.

See how the world’s largest militaries stack up in terms of active troop numbers.

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