Soon after Japan surrendered, the CCP was not in a good position. They had a lot people, but most were untrained, inexperienced and mostly unarmed. That's why they put the access to Manchuria on top of their list of things to do. Even at the end of 1947, Lin Biao was losing battle after battle and was about to disband his troops and hide in the forest. So based on their overall situation, Mao wanted sympathy from the international community and suggested democracy.
Vesicles, Lin Biao was only one of the commanders of the PLA. In the early stages of the Civil War, the CCP and the KMT were engaged in a seesaw of battles. Both sides won some and lost some.
全面内战爆发
1947年3月7日,政府代表张治中在南京送董必武等中共驻京人员乘坐美飞机撤回延安
1946年6月26日停战有效期刚过,國軍在劉峙、程潛的統率下,以20萬優勢兵力攻打在湖北、河南边界宣化店被包围的李先念部6萬中原解放军,李先念率部提前突围。大陆一般认为,解放战争从这时开始爆发。[22]。
7月,国共就苏北政权的谈判陷入僵局,此时国军为保卫南京侧翼安全,向苏中和苏北的新四军驻地发动进攻[23]。粟裕发起苏中战役,与国军激战从7月开始到12月底结束,连打七仗,粟裕部在运动战中歼灭了国军第69师,此次战役,共产党方面称为“苏中七战七捷”;而国军则占领了苏北全部城镇,把中共军队压过了陇海线。
在山西,解放军在7月下旬发起攻势。7月20日,解放軍为攻占大同,在应县与国军激战,始终未能攻克。8月,解放軍围攻大同。傅作义部全力增援大同守军,9月,傅作义第35军进攻集宁以解大同之围,此时国共在集宁处于胶着状态,大同又迟迟未能被中共攻克,故解放軍主动撤退。10月初,应马歇尔要求,国民政府下达第三次停战令,但停战令期限刚过,10月11日国军36集团军乘中共主力在大同之际,奇袭夺取了中共华北区中心城市张家口。正在斡旋国共冲突的的民主人士梁漱溟看到国军攻占张家口的报纸后称“一觉醒来,和平已经死去。”[24]
在山东,8月10日,刘邓三个纵队突袭陇海线,占领砀山和兰封之间百余公里铁路,随后国军调集大军反攻。9月初,解放军撤退的同时在定陶全歼国军整编3师,但是国军整体呈攻势的局势没有改变。在东线鲁西南地区,国军进展较为顺利,在晋南地区,胡宗南部队受阻,整1师第1旅被陈赓部围歼。10月下旬,国军占领25座县城,完成华北南线作战,中共晋冀鲁豫部队被压制在黄河以北。解放军的撤退让国民党误以为胜利在望。然而解放军人数实际上未减少,很快展开了反攻。
So I very much disagree with your assessment that the Communists were inexperienced and untrained. It is true that they were poorly equipped compared to the Nationalists. Jiang had access to vast amounts American military aid, while the Communists could only get their hands on what the Japanese left behind. However, the fact that they were able to hold their own against the Nationalists shows that they were all but "inexperienced and untrained".
This actually ties in to the Communists' contributions in the war against Japan. Remember that the Nationalists had access to American hardware by the end of the war against Japan. 1.2 million untrained peasants would have been only so much cannon fodder against WW2 weaponry. Therefore, it is clear that the communist troops were battle hardened and experienced veterans. How they gained that experience? There's only one logical answer to that.
Oh, and here's a page from a Taiwanese school book: