What was the root cause of the outbreak of the Second Opium War?

The root cause of the Second Opium War: The Great Powers further wanted to open the Chinese market and expand their interests.

The Second Opium War forced the Qing government to sign the Treaty of Tianjin and the Treaty of Beijing and the Treaty of Aigun and other peace treaties, and the invasion of the Great Powers went deeper. China thus lost more than 1.5 million square kilometers of territory in the northeast and northwest ****, after the war the Qing government was able to focus on the suppression of the Taiping Heavenly Kingdom, to maintain rule.

Expanded Information

The Second Opium War was a war of aggression against China jointly waged by Britain and France with the support of Russia and the United States. It was a war in which Britain and France, in order to further open up the Chinese market and expand their aggressive interests in China, took advantage of the Taiping Heavenly Kingdom movement in China and used the Yarrow Incident and the Ma Shenfu Incident as a pretext to join forces to attack the government of the Qing Dynasty.

Because the British and French used the Arrow incident and the Ma Shenfu incident as the pretext to start the war, it was called "The Arrow War" by the British. It was also known as the Anglo-French expedition to China or the Second Anglo-Chinese War.

The war is also known as the Second Opium War because it can be seen as a continuation of the First Opium War (i.e. the Opium Wars, as opposed to the Second).

In 1860, the British and French forces invaded Beijing, and when the Qing Emperor fled to Chengde, the British and French forces broke into the Yuanmingyuan and looted the jewels and burned it down. In the war, the Tsarist Russians came out to "mediate" and coerced the Qing government to cede more than 1.5 million square kilometers of territory, thus becoming the biggest winner. The war ended when the Qing government was forced to sign the Treaty of Beijing.

Reason for defeat: unfavorable preparations

In 1857, the British and French forces attacked Guangzhou, and the Qing government was too busy suppressing the Tianping Heavenly Kingdom to pay much attention to the battle. In April 1858, the British and French allied forces went north and provoked the first Battle of Dagu Kou, to which the Qing government still didn't pay enough attention, coupled with the backwardness of the equipment, leading to a disastrous defeat.

Waiting until June 1859, the second battle of Dagu Kou, the Qing government to give attention to the Sinhalese personally responsible for commanding the sea defense, plus the British and French allied forces are a bit gullible, only sent 12 warships to offend, after a fierce battle, the Qing army repelled the allied attack, defending the Dagu Kou.

From the second Battle of Dagu Kou, the British and French allied forces were not indestructible because they were temporarily formed and traveled a long distance. However, the Qing government was busy fighting the Taiping Army, coupled with paralysis. To a certain extent, this led to the fall of Guangzhou and the loss of the First Battle of Dagu Kou.

References:

Baidu Encyclopedia - Second Opium War