Why was Jing-mei’s mother’s life in China hard?

In the story "Two Kinds," we learn that Jing-mei's mother (Suyuan Woo) arrived in San Francisco after losing her parents, her home, her first husband, and her two twin baby girls in China during World War II. In the book The Joy Luck Club (from which the story "Two Kinds" can be found), we learn that Suyuan Woo's difficulties arose when the Japanese invaded China.
Accordingly, Suyuan's husband had sent her and their twin baby girls to Kweilin for safety. Suyuan's husband was an officer in the Kuomintang, so he could not stay with his family. Instead, he had to report to Chungking. Later, Suyuan and her babies fled Kweilin with nothing more than the clothes on their backs. A Chinese army officer had warned Suyuan that Japanese soldiers were coming to Kweilin. 
Suyuan first started out her journey to Chungking (where her husband was stationed) by pushing a wheelbarrow with her babies in them. Eventually, one of the wheels broke, and Suyuan had to carry the babies in slings. On each hand, she carried bags of food and two suitcases of clothing. Soon, her fingers bled from the exertion, and she had to continue without the bags and suitcases. The journey was onerous, and Suyuan and the babies suffered from hunger, thirst, and exhaustion. 
To make matters worse, Suyuan soon contracted a terrible case of dysentery. Fearing that she would soon die, Suyuan made the terrible decision to leave her babies by the side of the road. She attached photos of her parents and her wedding to the babies clothing. She also left money and jewelry under the babies' shirts and left a note imploring anyone who found them to care for them. 
Suyuan did not die, however; she was soon picked up by a truck heading to Chungking. There, she discovered that her husband had died, which added to her heartache. Suyuan eventually immigrated to America, but she never forgot her babies. Suyuan's life in China was hard because she had to endure physical suffering, the death of her husband, the loss of her parents, and separation from her twin baby daughters.