North Vietnamese victory depended on the supplies and reinforcements delivered by the Trail, which was located in the Kingdom of Laos.

An ongoing air campaign by the United States striking the Trail had little perceptible effect on the Communist logistics effort.

Nevertheless, Central Intelligence Agency (CIA) backed Laotian guerrillas and Royal Lao Army (RLA) military irregulars made further attempts at severing the Communist logistical lines of communication.

[2][3] By the end of April 1972, the Royal Lao Government (RLG) had lost control of the Bolovens Plateau and its overwatch of the Trail to the invading People's Army of Vietnam (PAVN).

Also, during the third week in May, the PAVN 39th Regiment unexpectedly made a rainy season advance to occupy the town of Khong Sedone on the banks of the Mekong River.

Champassak was to remain in Pakxe—barring cabinet meetings in Vientiane—overseeing Royalist efforts to regain Khong Sedone and block attacks on Pakxe.

King Savang Vatthana believed the operation should retake Paksong in the Communists' rear, cutting their supply lines into Khong Sedone.

[5] The RLG's immediate reaction was the dispatch of partially trained Bataillon Voluntaire 44 (BV 44) from Military Region 4, backed by four 105mm howitzers to retake Khong Sedone.

In early June, the Royalists began reinforcing the position with Thai mercenary troops returning from a loan to Military Region 2.

[6] In early June, Savannakhet Unit of the CIA planned Operation Black Lion to retake Khong Sedone.

On 15 June 1972, Groupement Mobile 32 (GM 32) was helilifted into Pakxe Site 47, unloading on the fly and without their heavy weapons company.

[8] The Communist defensive positions were laid out with a basic weakness; while antiaircraft guns and artillery pieces were sited on one bank of the Se Done River, most of their infantry protection was stationed on the other.

On 18 June, Alpha Group of GM 33 was repulsed in its attack on Phou Khong, being struck by artillery and mortar fire.

[9] However, during the second week in July, intercepted Communist signals traffic disclosed that the PAVN 39th Regiment had orders to hold the old RLA camp at all costs.

Even though intercepted radio messages revealed the PAVN was suffering heavy losses, the Communists hung on until 18 July before staging a fighting withdrawal over Phou Khong.

By 0100 hours on the 19th, all the Thai infantry was in full flight, as GM 401 abandoned its headquarters staff and the new fire support base.