Passage: By the time the Khmer Rouge initiated their dry-season offensive to capture the beleaguered Cambodian capital on 1 January 1975, the Republic was in chaos. The economy had been gutted, the transportation network had been reduced to air and water systems, the rice harvest had been reduced by one-quarter, and the supply of freshwater fish (the chief source of protein) had declined drastically. The cost of food was 20 times greater than pre-war levels and unemployment was not even measured anymore.Phnom Penh, which had a pre-war population of around 600,000, was overwhelmed by refugees (who continued to flood in from the steadily collapsing defense perimeter), growing to a size of around two million. These helpless and desperate civilians had no jobs and little in the way of food, shelter, or medical care. Their condition (and the government's) only worsened when Khmer Rouge forces gradually gained control of the banks of the Mekong. From the riverbanks, their mines and gunfire steadily reduced the river convoys bringing relief supplies of food, fuel, and ammunition to the slowly starving city (90 percent of the Republic's supplies moved by means of the convoys) from South Vietnam. After the river was effectively blocked in early February, the U.S. began an airlift of supplies into Pochentong Airport. This became increasingly risky, however, due to communist rocket and artillery fire, which constantly rained down on the airfield and city. The Khmer Rouge cut off overland supplies to the city for more than a year before it fell on 17 April 1975. Reports from journalists stated that the Khmer Rouge shelling "tortured the capital almost continuously," inflicting "random death and mutilation" on millions of trapped civilians.Desperate, yet determined, units of FANK soldiers, many of whom had run out of ammunition, dug in around the capital and fought until they were overrun as the Khmer Rouge advanced. By the last week of March 1975, approximately 40,000 communist troops had surrounded the capital and began...

Question: Who was the peace agreement with between the United States that did not work out?
Sihanouk