What unified combatant command is primarily responsible for civil support and homeland security?

The unified combatant command primarily responsible for civil support and homeland security is USNORTHCOM. This command has a significant focus on defense against threats to the U.S. homeland, which includes responding to natural disasters, ensuring the security of air, land, and sea borders, and coordinating civil support operations.

USNORTHCOM's mission encompasses both military and civil components, enabling it to work closely with federal, state, and local agencies during times of crisis or incidents that require a coordinated response. This includes providing assistance to civil authorities, ensuring that military readiness is aligned with homeland defense strategies, and executing operations that support national interests within the United States.

Other commands like USSOCOM focus primarily on special operations, while USAFRICOM and USEUCOM are centered on specific regional military engagements and partnerships, making them less aligned with domestic civil support and homeland security roles. Therefore, USNORTHCOM stands out as the correct answer for this question regarding its specific responsibilities.