Original question by u/XiahouMao (https://www.reddit.com/r/threekingdoms/comments/knt1ia/so_what_really_happened_to_cao_ang/)

My analysis:

Is Cao Ang's image of filial piety a manufactured one?

Probably not.

In Weilue (or The Brief of Wei),

Cao Pi said [in front of his ministers], 'my elder brother [Cao Ang] was nominated as the Filial and Incorruptible candidate, he deserved to inherit the throne. If [Cao Chong] was still here, I would not take over the world either.'

《魏略》曹丕:「家兄孝廉，自其分也。若使仓舒在，我亦无天下。」

• Note that Cao Cao and Cao Ang were the only persons in Cao's family who received the nomination.

• However, it would not be surprising if Cao Cao (not Cao Ang) paid for his own nomination. Cao Cao's father Cao Song offered 1 billion bribe to an eunuch in order to purchase a title equivalent to a 5-Star General (後漢書曹騰傳：｢嵩，靈帝時貨賂中官、及輸西園錢一億萬，故位至太尉。｣).

Is there any possibility that Cao Ang was 'abandoned' by Cao Cao?

It can be possible, but I disagree.

Cao Cao expressed his remorse regarding Cao Ang's death in several occasions. These conversations implied that Cao Cao really loved his son Cao Ang.

In All Essays of Jin,

Cao Cao said, '[Cao Chong/Ang's death?] has been my regret, but it is also your (i.e. every sons who is alive) fortune' (thanks to u/ohhyyy for correction).

《全晋文》曹操:「此我之不幸, 而汝曹之幸也。」

• Note that Cao Pi would never come close to the throne if his elder brothers Cao Ang or Cao Chong did not die. Cao Pi’s brothers were considered better candidates to inherit the throne (ability-wise and ranking-wise).

• Note that Cao Cao made that statement after Cao Chong's death, it is unclear whether he was upset that all his elder sons were dead (thanks to u/vnth93 and u/10thousand_stars for bringing up).

In Weilue,

Cao Cao later became very sick, felt concerned and could not get out of bed, he sighed, 'I never feel sorry/regret for what I have done in my life. If there is after-life and Cao Ang asks me "where's my (step-)mum", how should I answer him!'.

《魏略》:「後太祖病困，自慮不起，嘆曰：“我前後行意，於心未曾有所負也。假令死而有靈，子脩若問‘我母所在’，我將何辭以答！”」

• Note that Miss Ding (Cao Ang's step mother, Cao Cao's legal wife) was very pissed at Cao Cao and blamed him for killing Cao Ang (《魏略》:｢將我兒殺之，都不復念！」).

• Despite Cao Cao's numerous attempts to explain the situation, Miss Ding refused to listen/accept. Later, Cao Cao sent her back to her parent's home so that Miss Ding could calm down. Although Cao Cao visited her later, Miss Ding refused to settle with Cao Cao and they divorced subsequently.

How did Cao Ang die eventually?

• Cao Ang did not die immediately after he gave up his horse for his father. Note that Zhang Xiu's rebellion happened at Wan, but Cao Ang died at Rang (《魏略》:「子脩亡於穰」). The distance between the two counties is around 55km.

• One of the plausible explanations is that Cao Ang was captured by Zhang Xiu and sent to Rang. However, Cao Ang did not recover from serious injury, and died subsequently.

• This explanation aligns with the fact that Zhang Xiu immediately chased after Cao Cao when Zhang Xiu led a successful rebellion at Wan (《裴松注》:「公乃引兵還舞陰，繡將騎來鈔」), since Cao Ang was captured. And of course, the explanation has no solid evidence due to lack of information.