Final answer:
In 1918, European nations replaced tired fighters with laborers from other countries and workers from different regions, such as African Americans in the United States. Recruitment efforts were expanded to include diverse groups.
Step-by-step explanation:
In 1918, European nations started to run out of men to recruit for the war. To replace the tired fighters of Europe, various strategies were employed. One method was to enlist laborers from other countries, such as China. Approximately 130,000 Chinese laborers were brought to Europe to repair equipment and dig trenches, but they were not sent to fight. Another replacement for tired fighters was the recruitment of workers from different regions. For example, during World War I, factories in the manufacturing belt of the United States recruited African Americans from the South to fill the jobs left vacant by men serving in the military. Additionally, efforts were made to expand the army and recruit new soldiers from different backgrounds. In the United States, recruitment efforts were expanded to include African Americans, women, Native Americans, and Japanese Americans.