Learn how to keep your forces ready for anything the world throws at you.

Land Units comprise the majority of your Army.

There are melee units like the warrior, ranged units like the crossbowman, and Light and Heavy Cavalry like the Horseman and the Knight.

There are also more specialized units, like the Recon, Siege, and Anti-Cavalry units.

Most units take and receive damage during combat.

Ranged units like Slingers cause damage at a distance so they aren't damaged on their turn, but they are weak to melee attacks and don't restrict enemy movement.

Siege units like Catapults aren't very good at combat but excel in defeating cites.

A well rounded military will also have Naval units, which can be melee, ranged, or raider units, and eventually an Air Force with Fighters and Bombers.

Support units like Medics and Observation Balloons enhance your military units.

Attaching a combat unit to these units also provides them with defense from capture.

Great Generals and Admirals can also be attached to combat units for passive damage and movement bonuses.

A unit gains experience points for engaging in combat.

Experience points are used to promote the unit, which allows you to pick a new ability for it.

Promotion also heals the unit, but promoting a unit uses all its movement points that turn.

As you discover new technologies, you'll be able to upgrade the unit to a new type, such as upgrading a basic warrior into a more powerful swordsman.

This costs gold and also uses all movement points for that unit for that turn.

Units have maintenance costs in gold.

You can find how much each unit costs to maintain in the Civilopedia.

Make sure you have a strong economy if you want a large military or your units will disband.

Eventually you'll be able to form units into Corps and even Armies, which combine the strength of multiple units into a single unit while keeping its maintenance cost low.

You can also use the Conscription and Levee en Masse Policies to reduce unit maintenance costs.

Spies are extremely specialized units that allow you to conduct espionage in enemy cities.

These activities range from allowing more diplomatic visibility to sabotaging industrial zones to stealing great works.

You can also place them in your own cites to counter other civs' Spies.

Unlike any other unit, spies can be captured.

If this happens they can be traded back to their original owner via diplomacy.

Teddy Roosevelt says you should speak softly and carry a big stick.

Know how to use your army in Sid Meiers' Civilization VI.