Short answers, pulled from the story.
Operation Ichi-Go had two primary goals: capturing American air bases in south-east China from which US bombers were attacking the Japanese homeland and shipping, and opening a continuous overland rail route through China to French Indochina for transporting raw materials from south-east Asia. The objectives were approved by Emperor Hirohito on the 24th of January 1944.
The Imperial Japanese Army mobilized 500,000 troops, 100,000 horses, 1,500 pieces of artillery, 800 tanks, 15,000 mechanised vehicles, and 200 bombers for Operation Ichi-Go. Historian Hara Takeshi described it as the largest military operation ever carried out in the history of the Japanese army. The force was supplied with eight months of fuel and two years of ammunition.
Chinese military effectiveness had sharply declined by 1944 due to economic collapse, corruption, reduced military readiness, and poor command and control. The local population in Henan, alienated by wartime deprivation and army requisitions, withheld support and in some cases attacked Chinese troops. American diplomat Clarence E. Gauss had warned Washington of the imminent offensive, but China's best troops were redirected to the Burma campaign under US Lend-Lease pressure.
General Joseph Stilwell was relieved as Chief of Staff to Chiang Kai-shek and as commander of US Forces, China Theater following a confrontation over command authority during Ichi-Go. Stilwell had delivered a Roosevelt ultimatum demanding unrestricted command of all Chinese forces; Chiang refused and demanded his replacement. Major General Albert Wedemeyer took over Stilwell's role, and Stilwell's other responsibilities across the China Burma India Theater were divided among other officers.
According to historian Cox, China suffered approximately 750,000 casualties in Operation Ichi-Go, including soldiers killed, captured, rendered combat ineffective, and those who simply melted away from their units. The First War Zone alone lost as many as 100,000 troops in the Henan phase. Japanese deaths totaled approximately 100,000 by the end of 1944, including those who died of illness.
Operation Ichi-Go accelerated the deterioration of Nationalist military and political credibility while enabling Chinese Communist guerrillas to expand their influence in the areas of social confusion the campaign created. Historian Hans van de Ven argues that Ichi-Go's political impact on China was as important to the post-war world order as Operation Overlord and Operation Bagration were in Europe. Nationalist corruption, economic collapse, and popular alienation following Ichi-Go contributed to the Communists' eventual victory in the resumed Civil War after World War II.