借這個標題問一下，根據英文維基百科的資料所述：
https://en.wikipedia.org/wiki/Wang_Jian_(Qin)
裡面有一段：
The first Qin invasion initially appeared successful but ended up in a major
disaster when the 200,000 Qin army was annihilated by a combined attack of
500,000 Chu troops led by General Xiang Yan and another army under the direct
command of Lord Changping, at the Battle of Chengfu in the unfamiliar
territory of Huaiyang(modern-day northern Jiangsu and Anhui provinces).
意思是項燕跟昌平君聯合的楚軍，人數多達50萬人。
這樣的話跟秦軍60萬人相比，也差不了太多。
就算這50萬人是有把軍伕、軍眷計算在內，但秦軍內不是也可能有軍伕軍眷嗎？？
這樣楚軍在兵力上應該沒有與秦軍差太多。而且該文下面又記載：
In 224 BC, Wang Jian began the second invasion of Chu. Chu's morale had
greatly increased after their success the previous year. The Chu forces were
content to wait and defend their territory.
意思是楚軍在前一年擊敗李信所率的秦軍後，士氣得到很大提升。
這樣看來楚軍在兵力並不居劣勢，且從前一年對秦軍作戰中得到經驗、士氣。
而且楚國腹地廣大，如果採用像早先李牧對秦軍那樣的戰術：
也就是以堅強防守消耗秦軍、並且故意放棄一些據點、路線，誘使秦軍孤軍深入，
等到秦軍完全進入楚軍的陷阱中再發動反擊。
這樣楚軍有機會反敗為勝嗎？史實上趙軍利用這個戰術也確實擊敗過秦軍：
https://en.wikipedia.org/wiki/Battle_of_Fei_(233_BCE)
Li Mu felt that the Qin army's morale was high after its earlier victories,
so it would be unwise for Zhao to attack Qin then. He ordered his troops to
strengthen their fortifications and defences while waiting for an opportunity
to launch an counteroffensive.
Li Mu predicted that Huan Yi would retreat from Fei to save the camp, he
ordered his men to lay an ambush on Huan Yi's retreat route. Huan Yi's
retreating troops fell into the ambush. Qin sustained over 100,000 casualties
in the battle and its army was almost completely wiped out.
只是因為趙國腹地比較小，比較沒有空間一直使用這種戰術。但是從西元前236年鄴之戰
到西元前228年邯鄲淪陷，趙軍也支撐了8年之久：
https://zh.wikipedia.org/wiki/%E7%A7%A6%E6%BB%85%E8%B6%99%E4%B9%8B%E6%88%B0
而楚國領土廣大，有足夠戰略縱深，應有能力執行這種戰術。
而且楚軍即使有數十萬人，也不可能處處都設防，而使用這種機動靈活的方式來防守，
可集中兵力，解決處處設防兵力分散的問題。
那麼楚軍有可能擊敗入侵的秦軍，至少保住半壁江山呢？？
還是其實楚軍是做不到這種程度的戰術，要楚軍做到這樣其實是高估楚軍的戰鬥力？？
而且楚軍陣營沒有像是李牧這樣的將領，所以楚軍被秦軍擊敗是必然的？？