Headquarters is a mode in which teams contend over a Target Area as well as a Core near each team's deployment area.
Each round is divided into an Area Capture Phase, in which the teams try to take said area, and a Core Assault/Defense Phase, in which a core must be attacked or protected.

Area Capture Phase

In this phase, the goal is to secure a target area on the map.
There is only one such target area. Each team must try to secure it.

You capture the target area by entering it and maxing out the Capture Meter.
The target area is secured upon maintaining control of the area for a set amount of time and reaching a Capture Rate of 100%. Then, the Core Assault/Defense Phase begins.

The team which succeeds in securing the Target Area in the Area Capture Phase receives 1 point.

Core Assault/Defense Phase

In this phase, both teams' roles change.
The team that secured the target area must try to destroy the enemy team's core and the other team must try to protect it.

Destroying the Core

The team trying to destroy the core will need to lower the core's durability by attacking it.
When the core's durability reaches 50% it will become temporarily invulnerable.
After a while, it will lose its invulnerability and attacks will work again. Getting its durability to 0% will destroy it.

During the Core Assault Phase, you will get 1 point for reducing the core's durability to 50%, and 1 point for destroying it after its invulnerable period.

Defending the Core

The team tasked with defending their core, located near their deployment area, must defend it from enemy attacks until the time limit is up.

During the Core Defense Phase, if the defenders' core has any durability remaining when the round ends, they receive 1 point.

Rules Guide (explanatory video)

EXTRA TIME

In each of the phases, if certain conditions are met when the time limit is up, you'll go into Extra Time and the game will continue.

Victory Conditions

The first team to earn 5 points by the fifth and final round is the winner.
When either team reaches 5 points, the round will end and the outcome will be decided.

If neither team reaches 5 points by the fifth round, whichever team has the most points at the end of that Core Assault/Defense Phase is the winner.

Draws

If both teams have the same number of points at the end of the fifth round's Core Attack/Defense Phase, a draw is declared.

*There are no overtime rounds in this mode.