The 1st and 2nd Battalions, 299th Infantry were federally activated in 1968 to support the United States Army Pacific during the Vietnam War.

After the draft and activation of 1940, the makeup of the 299th changed dramatically, with a mix of Hawaiian, White, Japanese, Chinese, Portuguese, Puerto Rican, and other races.

Despite some pushback from Washington DC, the multiethnic unit provided support for its active duty counterparts in Hawaii.

Although the initial activation was only supposed to last for 12 months, it was extended in October 1941, much to the chagrin of many of the men who were federalized and taken away from their civilian jobs and families.

In the aftermath of Pearl Harbor, the 299th Infantry Regiment was guarding the outer islands from possible invasion by the Empire of Japan.

Following December 7, 1941, The 299th Infantry enforced Martial Law across Hawaii Island, Maui, Molokai, and Kauai.

On the night of December 30, 1941 the Japanese submarines launched a coordinated strike on Hilo, Hawaii, on Kahului, Maui, and Nawiliwili on Kauaʻi.

On January 28, 1942, the US Army Transport Ship Royal T. Frank, was bringing 26 soldiers of the 299th Infantry back home to Hawaii Island after finishing their basic training, which had been interrupted by the attack on Pearl Harbor.

Covered in oil, the survivors spent hours in the ocean, many clinging to whatever debris they could, before they were picked up by the ammunition barge that had been the actual target of the Japanese submarine.

Relief from the mainland finally started to arrive in March 1941, and the 299th Infantry began to transition to Scofield Barracks for service.

[3]: 212  These Hawaii Nisei (Japanese-Americans) would form the famed 100th Infantry Battalion later attached to the 442nd RCT and would fight heroically in Europe becoming the most decorated unit of its size in World War II.

The 2–299th IN, commanded by LTC Kenneth Hara, began train-up at Schofield Barracks before moving to Ft. Bliss in October 2004.

In January 2005 the battalion completed combat certification at JRTC in Ft. Polk, and began arriving in Iraq in February.

In addition, the battalion was also responsible for security in the areas and neighborhoods surrounding Camp Victory (such as Al Furat, Makasib and parts of Route Irish) conducting patrols and cordon and search missions to capture, kill, or disrupt the enemy insurgents in the area.

When the 2–299th Infantry returned from Iraq they began the process of being re-flagged into a reconnaissance squadron under the command of LTC Kenneth Hara.

As "Task Force Koa," the squadron was commanded by LTC Rudolph Ligsay and CSM Craig Ynigues.

TF Koa conducted convoy escorts from logistical bases in Kuwait, into and throughout the entire Iraq Theater of Operations.

In November 2012, senior officers, non-commissioned officers, and some enlisted soldiers of the 1–299th Cavalry were selected and deployed forward to Afghanistan as security forces advisor teams (SFAT) as part of a group pooled from the 29th IBCT to train the Afghan National Security Forces.

The SFAT advisors were distributed throughout southern Afghanistan in support of the Afghan National Security Forces and ISAF initiatives in the Regional Command-South.

In October 2018, the 1-299 Cavalry, commanded by LTC John Udani and CSM Shon Antolin, were deployed as Peacekeepers to the Sinai, Egypt as part of the Multinational Force and Observers (MFO) mission.

Rather than wearing the United Nations’ blue beret and helmet cover, the MFO is an independent peacekeeping organization.

The unit was split in two with LTC Udani taking charge of South Camp with HHT and C Troop as part of the MFO's Southern Battalion (SOUTHBATT).

In the Southern portion of Zone C of the Sinai Peninsula, the 1-299 Cavalry, was joined in SOUTHBATT with Fijian and Australian Defence Force Members.

In the Northern half of Zone C of the Sinai Peninsula, the 1-299 Cavalry Soldiers in the North were taken charge by MAJ Kawika Hosea, the Squadron Executive Officer.

A detachment of HHT Staff and B Troop, were placed at FOB North where they were tasked with providing security and command and control of MFO and US assets as part of the Northern Battalion (NORTHBATT) Staff and B Troop as part of the FOB North Response Team.

The unit served as the head of MFO missions in the Northern Sinai and provided security of FOB North.

As the Egyptian Armed Forces were combatting insurgents in the Northern Sinai, the unit was on a heightened alert throughout their tour having to carry their weapons even while off duty.

There were minor contact with insurgent forces by the MFO, but it remained a neutral observer to ensure the peace between Egypt and Israel.

1-299 CAV provided security for dignitaries during the Asian Pacific Economic Cooperation conference in November 2011, protecting routes and locations for delegations from the 21 member economies as they met in Honolulu, Hawaii.