"To subdue the enemy without fighting is the acme of skill."
2500 years ago, Sun Tzu said that to defeat your enemy without using force is the acme of skill. So, how does one do this? It involves the use of various arts of statecraft that are not well-cultivated in the United States. But the Russians have long cultivated them.
During the Cold War, the Russians conducted various types of covert and overt influence operations using agents of influence, disinformation, and forgeries (together called "active measures"), as well as propaganda, and offensive counterintelligence operations. Their targets included: the national strategic leadership of NATO countries, as well as of other countries throughout the world; various non-governmental groups that had influence over governmental decision-making; the media, including the film industry; educational institutions at all levels; churches; unions; and the public at large.
Putin’s regime has not forgotten these techniques. It has been using them blatantly in its attempts to annex Crimea and pry off several other provinces from Ukraine. It has been using agents of influence to corrupt the decision-making of many of its neighboring countries. It has used its intelligence services to bribe members of Parliament and other government officials in these countries.