During WWII, the US helped Chinese Nationalists resist the Japanese.  Soon after the war, Communist rebels took over China.  Did the US assist or resist communists taking over China?  Wikipedia seems to disagree with my colleague Gordon Tullock.  Wikipedia says:

The Soviet Union provided limited aid to the Communists, and the United States assisted the Nationalists with hundreds of millions of dollars worth of military supplies and equipment (now surplus [Communist] munitions), as well as the airlifting of many Nationalist troops from central China to Manchuria.

Wikipedia elaborates:

In Manchuria the Japanese surrendered to the Soviet Union. … [Soon after] the 700,000 Japanese troops stationed [there] surrendered. … [Nationalist leader] Chiang Kai-shek realized that he lacked the resources to prevent a [Communist] takeover of Manchuria following the scheduled Soviet departure.  He therefore made a deal with the Russians to delay their withdrawal until he had moved enough of his best-trained men and modern material into the region. [Nationalist] troops were then airlifted by the United States to occupy key cities in North China, while the countryside was already dominated by the [Communists]. The Soviets spent the extra time systematically dismantling the extensive Manchurian industrial base (worth up to 2 billion dollars) and shipping it back to their war-ravaged country. …

The total Soviet weaponry and Japanese weaponry captured by the Soviet Union that was given to the communists was only enough to equip … a mere 20,000 communist troops out of a total of 400,000 … and the Soviet aid to Communists completely stopped by the end of 1947. … The United States assisted the [Nationalists] with hundreds of millions of dollars worth of new surplus military supplies and generous loans of hundreds of millions of dollars worth of military equipment. 

But in chapter 3 of his book Open Secrets of American Foreign Policy, my colleague Gordon Tullock, an almost-Nobel-winner who was back then a US diplomat stationed in China, paints a different picture:

With the collapse of Japan and the invasion of Manchuria by Russia, everyone tried to occupy the newly vacated areas.  The Communists withdrew the bulk of their forces into Manchuria where they were re-equipped by the Russians, mainly with Japanese arms. … The nationalists then moved north and invated Manchuria.  The Communists tried to stop them and at Su Pin Kai the Nationalists won a major victory.  The United States quickly slammed an arms embargo on the Nationalists.  What led General Marshall to do this has never been explained.  …

I remember seeing a newsreel in which reporters asked President Truman why he was trying to set up a coalition with the Communists in China and trying to prevent similar coalitions in France and Italy.  He responded simply by saying that a coalition between the Nationalists and Communists in China was very important … Chaing, now being short of ammunition, sopped his offensive in Manchuria and began efforts to negotiate a coalition with the Communists, essentially because he thought it was necessary for even reasonably good relations with the United States.  He even arraigned to elect a national assembly.  The embargo stayed on.  The communists, having plenty of ammunition, refused to negotiate on a coalition, and switched to the offensive. … The embargo … was only relaxed after the outbreak of war in Korea. …

I sometimes hear that the United States gave the Nationalists $10 billion in arms after the Japanese surrender. … All of the equipment left on the Pacific Isles when our troops went home was given to the Nationalists about two years later. … It was … auctioned off to junk dealers in the United States … total receipts from the auctions was about $200 million.  Since this money was in the United States, it was subject to the embargo and could not be used to buy … military supplies. 

Tullock goes on to describe how US diplomats in China personally favored the communists.  Even if the truth is somewhere between these pictures, it seems quite at odds with the usual US-fighting-communism story.