Why do Winston and Vincent most likely stop playing chess with Waverly? (Paragraph 30)

Hurry 20 mins all the animals were now present except moses, the tame raven, who slept on a perch behind the back door. when major saw that they had all made themselves comfortable and were waiting attentively he cleared his throat and began: "comrades, you have heard already about the strange dream that i had last night. but i will come to the dream later. i have something else to say first. i do not think, comrades, that i shall be with you for many months longer, and before i die i feel it my duty to pass on to you such wisdom as i have acquired. i have had a long life, i have had much time for thought as i lay alone in my stall, and i think i may say that i understand the nature of life on this earth as well as any animal now living. it is about this that i wish to speak to you." which historical figure does old major most likely represent? tsar nicholas ii an imperial guard vladimir lenin joseph stalin