Churchill is saying that when Stalin took over the country ("inherited" it from Lenin, I think), Russia was a very primitive backward place with little industrialization symbolized by wooden ploughs on every farm (probably pulled by horses, or even humans). There were no tractors or other types of advanced machinery. By the time Stalin died, the country had achieved tremendous technological advances including not just tractors and other machinery, but nuclear bombs. I hope that helps.

The writer is quoting Churchill. Churchill is saying that Russia made incredible progress in industrialization and technology under Stalin. "Stalin inherited Russia..." He "got" Russia (from Lenin), like a child inheriting something when their father dies. When he started, Russia was a rural nation. Many farms, few factories. Churchill exaggerates to make a point. He says the most advanced machines Russia had were wooden ploughs of the kind that had been used for centuries. Before Stalin, Russia had wooden ploughs. After Stalin, Russia was "in possession of" atomic weapons. The phrase "with A wooden plough" uses the singular form. It is rhetoric. It is a short way of saying "Russia had only very crude, simple, old-fashioned machines like wooden ploughs. It did not have modern technology, like gasoline-powered tractors." He is imagining all of Russia symbolically. He is talking as if all Russia was one person--one farmer with ONE crude wooden tractor. Stalin didn't leave the plough. Stalin left Russia. Stalin didn't have atomic bombs. Russia had atomic bombs. First Russia had wooden ploughs. Then Russia had atomic bombs. Stalin gave Russia modern technology. The writer of the passage hates Stalin. He is trying to explain why some Russians approve of Stalin. The writer thinks it is crazy to admire Stalin. He writer admits that Stalin deserves credit for modernizing Russia. That was a good thing Stalin did. THEN in the next sentence the writer turns around. He says Stalin deserves a lot of BLAME. In order to make progress, he did terrible things. I will try to summarize the meaning of the passage. "1) It is crazy that any Russians admire Stalin. 2) They say Stalin was good because he modernized Russia. He took it from wooden ploughs to atomic bombs. 3) But the bad things Stalin did were much worse than the good things he did."