Passage: In 1912, Russian advisers to the Bogd Khan set up a military school at Khujirbulan, and Sükhbaatar was one of the soldiers transferred there. His talent for military tactics and his skills at riding and shooting earned him the respect of his comrades, and after the training he became a platoon leader of the machine gun company at Khujirbulan. In 1913, he set up his own household with his wife Yanjmaa. They had had their first son in 1911, but Yanjmaa's parents objected to the relationship on the grounds that Sükhbaatar was too poor.

Question: When did the platoon leader have his first son?
1911