June 1954: The Geneva Peace Accords recognize Cambodia with “full independence and sovereignty.” Prince Sihanouk embarks on a policy of neutrality.{256}
1960-1963: Cambodia faces increased border clashes with South Vietnam and Thailand. Relations sour between the US and Cambodia.
1963: Sihanouk terminates formal relations with the US and South Vietnam
1964-65: South Vietnam verges on collapse, introduction of conventional US ground forces to the war. Sihanouk permits VC to expand border sanctuaries in Cambodia.
1966-67: Cambodia opens formal diplomatic relations with Hanoi. Port of Sihanoukville opens to arms and supply shipments destined for Communist forces in South Vietnam. General Westmoreland denied permission to attack border sanctuaries as situation stabilizes in South Vietnam. Salem House patrols begin into Cambodia. Roughly 1300 patrols are conducted prior to the incursions.
January-June 1968: Tet Offensive and aftermath. Communists suffer severe losses but convince US public that the Vietnam War cannot be won. Lyndon Johnson refuses to run for reelection.
November 11, 1968: Richard M. Nixon elected President on a “Peace with Honor” platform promising a military withdrawal from Southeast Asia.
March 1969: Menu bombings secretly commence in Cambodia. 3,874 sorties follow between March 18, 1969, and May 26, 1970.
July 1,1969: President Nixon formally initiates Vietnamization.
July 1969: COSVN Resolution Number 9 articulates NVA post-Tet strategy of disruption of the US withdrawal and Vietnamization plan.
March 1970: Cambodian Prime Minister Lon Nol launches an anti-Vietnamese campaign and seizes power on March 18.
April-May 1970: Planning and execution of Rockcrusher and related attacks. NVA conducts “Campaign X” offensives against the Lon Nol regime. Elements of four NVA/VC divisions expand base areas, seize much of northeastern Cambodia, and threaten Phnom Penh. Atrocities against ethnic Vietnamese by Lon Nol's forces occur in Cambodia.
April 14: ARVN units from III CTZ conduct three-day raid (Toan Thang 41) against sanctuaries in Angel's Wing sector of Cambodia.
April 19: General Abrams informs field force commanders to prepare contingencies for cross border attacks into Cambodia. Planning begins for operations Toan Thang 42 through 46.
April 29: Toan Thang 42 launched under ARVN control against sanctuaries in Parrot's Beak section of border. Phase I (preparation) initiated as 1st Cavalry Division reports Task Force Shoemaker prepared for initial operation into the Fishhook border region. Units move into final staging areas.
April 30: The administration delays execution of Toan Thang 43 (Fishhook) to coincide with Presidential address to the nation. Units conduct final combat preparations. Elements from the 25th ID (2-47 Mech, 2-34 Armor, 3-4 Cav) come under operational control of Task Force Shoemaker.
May 1: Early morning ARCLIGHT and artillery strikes precede ground advance concluding Phase I. Phase II (assault) commences at 0730 as TF Shoemaker crosses line of departure. First ground units cross into Cambodia at 0945. By nightfall, 3d ARVN Airborne Brigade establishes LZ East and Center in Cambodia. US troops secure LZ X-Ray. LZ's converted to firebases by the following morning. First significant cache discovered by 3d ARVN. Enemy contact is light throughout zone of attack. 1-9 Air Cav destroys several NVA elements attempting to evacuate area.
May 2: Phase III, exploitation of initial allied assault begins. 6 additional ARCLIGHT strikes impact in Fishhook. 11th ACR links up with 9th Battalion of 3d ARVN Airborne Bde. 11th ACR reaches Highway 7 by the afternoon. Allies discover numerous small-and medium-sized caches. l-9th Air Cav discovers “the City.” NVA avoid contact.
May 3: 1-5 Cav investigate “the City” discovering the third largest cache of the operation. l-9th Air Cav continues to screen along the 25-mile limit of advance, destroying additional four enemy convoys. NVA and VC begin limited attempts to disrupt allied attacks. 11th ACR(-) reaches Highway 7. II FF alerts 25th ED to prepare to attack into base area 354.
May 4: II FF realigns boundaries giving 25th ID the western third of the Fishhook. TF Shoemaker expands to include elements of 1st Bde, 1st Cav and 1/11 ACR. 11th ACR receives orders to seize Snoul and begins attack along Route 7. Destroyed bridges slow advance of 11th ACR. Evacuation and destruction of captured supplies begin at “the City” by l-5th Cav.
May 5: Task Force Shoemaker stood down. All forces revert to 1st Cav control to continue operations. 5-12th Inf Bn, 199th Light Infantry Bde becomes OPCON to 2d Bde, 1st Cav. 2/11 ACR seizes Snoul after defeating the 141st NVA regiment in heavy fighting. Units continue search and destroy operations in areas of operations. Several additional caches are discovered. In II CTZ, the 4th ID attempts to launch Operation Tame the West until turned back by heavy fires at the projected LZ's.
May 6: Phase IV (Expansion of search, destroy and evacuation operations) begins. II FF and ARVN III Corps order three additional attacks into base areas. The 25th ID conducts operation Bold Lancer (Toan Thang 44) to locate caches in Base Area 353. 2d Bde, 1st Cav initiates Toan Thang 45 against Base Area 351. 9th ARVN Infantry Regiment conducts Toan Thang 46 against Base Area 350. To the south, ARVN forces seize Chup rubber plantation in Parrot's beak operations (Toan Thang 42). In II CTZ, 4th ID reinitiates Tame the West after additional preparatory fires and seizes initial objectives.
May 8: D Co, 2-12 Cav discover “Rock Island East,” the largest cache of the war, during Toan Thang 45 assault. ARVN units in Toan Thang 46 meet coordinated NVA resistance. COSVN begins evacuating from Base Area 353. US intelligence confirms location of COSVN.
May 9: The 25th ID expands Bold Lancer in an effort to seize COSVN. ARCLIGHT strikes alert COSVN personnel of impending assault. Most COSVN personnel move out to the west hours prior to US arrival. Assessment and evacuation begins of “Rock Island East.” Operation Cuu Long initiated by ARVN to destroy Mekong Delta base areas. In conjunction, South Vietnamese/US Navy flotilla evacuate ethnic Vietnamese from Cambodia.
May 13-14: II FF realigns the tactical area of responsibility. 2-34 Armor and 2-47 Mech revert back to 25th ID. 1st Cav extends boundaries east, 25th ID controls western half of Fishhook. 9th ARVN Regiment assumes control of south of Fishhook. 5-12th Inf Bn OPCON to 2d Bde/1st Cav from 199th Light Inf Bde, assumes security of FSB Brown. FSB Brown assaulted by 174th NVA regiment. US forces repel the assault with heavy NVA losses.
May 16: D Company, 1-12 Cav repels an enemy assault on FSB Ranch. 4th ID concludes Operation Tame the West in II CTZ.
May 19-20: II Field Force AO realignments remove 1st Cav from Fishhook to fully support Toan Thang 45.
May 21 : ARVN troops in Toan Thang 46 discover a major hospital complex after heavy contact.
May 23: 5-7 Cav Bn discovers “Shakey's Hill,” the second largest cache of the operation.
June 5-20: Numerous small to medium sized caches discovered in all AOs. Engineers complete road networks to support cache evacuations of Shakey's Hill and other caches. Enemy contacts and mining incidents increase throughout Fishhook. Monsoon rains begin to severely restrict mobility of heavy forces
June 15: 28 NVA killed in an assault of FSB David in 1st Cav AO.
June 20 Phase V (withdrawal) commences for Toan Thang 43 and 46. US forces conduct sequenced withdrawal supported by covering artillery and air support.
June 21-28: US forces continue evacuation and redeployment to South Vietnam. 1st Cav units continue to discover small and medium sized caches. Most are destroyed in place. Rome Plow and demolition operations destroy NVA bunkers and cache sites. Firebases are relocated to ensure continuous support of the mission. Allied forces report little contact throughout sector.
4:00 p.m., June 29: Elements of 3/11 ACR reenter South Vietnam as the last ground forces out of Cambodia.
5:28 p.m., June 29: 1-9 Air Cav withdrawals last heliborne forces out of Cambodia.
6:00 p.m., June 29: II FF deadline for all US troops out of Cambodia
June 30, 1970: US ends ground and advisory support of Toan Thang 42 and 46, Operations Tame the West and Cuu Long. ARVN units continue operations on reduced scale.
July 1970: NVA and VC forces begin rebuilding the Cambodian sanctuaries. Attacks against Lon Nol and ARVN forces in Cambodia increase. Ho Chi Minh network expands.