MOSCOW—Russia’s defense ministry says the troops that were deployed to Kazakhstan as violent demonstrations shook the country have returned home. The troops were part of a force sent as peacekeepers by the Collective Treaty Security Organization, a Russia-led military alliance of six former Soviet states. The CSTO approved the force of more than 2,000 on Jan. 5 at the request of Kazakh President Kassym-Jomart Tokayev. The Russian Defense Ministry said Saturday that all of its planes carrying troops had returned. It was not clear whether troops from other CSTO countries remain in Kazakhstan. The demonstrations started on Jan. 2 to protest a sharp rise in fuel prices. They spread quickly from the western part of the Central Asian nation to more populous areas, eventually reaching its largest city of Almaty, and grew into violence within several days. But something changed over the course of a week—groups of armed men appeared …