structural:reformatting, structural:summarization
Desertions

Desertion was a major problem for both armies. In the Mexican Army, desertions depleted forces on the eve of battle. Most soldiers were peasants who had a loyalty to their village and family but not to the generals who had conscripted them. Often hungry and ill, underequipped, only partially trained, and under-paid, the soldiers were held in contempt by their officers and had little reason to fight the Americans. Looking for their opportunity, many slipped away from camp to find their way back to their home village.

The desertion rate in the U.S. Army was 8.3% (9,200 out of 111,000), compared to 12.7% during the War of 1812 and usual peacetime rates of about 14.8% per year. Many men deserted to join another U.S. unit and get a second enlistment bonus. Some deserted because of the miserable conditions in camp. It has been suggested that others used the army to get free transportation to California, where they deserted to join the gold rush; this, however, is unlikely as gold was only discovered in California on January 24, 1848, less than two weeks before the war concluded. By the time word reached the eastern U.S. that gold had been discovered, word also reached it that the war was over.

Hundreds of U.S. deserters went over to the Mexican side. Nearly all were recent immigrants from Europe with weak ties to the U.S. The Mexicans issued broadsides and leaflets enticing U.S. soldiers with promises of money, land bounties, and officers' commissions. Mexican guerrillas shadowed the U.S. Army and captured men who took unauthorized leave or fell out of the ranks. The guerrillas sometimes coerced these men to join the Mexican ranks.