In Civ V, you've got to choose where you place units carefully, and you have to pay close attention to where enemy units are. In my most recent game, I went to war with the Japanese and we had only a three-tile border, so I had to move my large army through a narrow bottle-neck while also contending with Japanese counter attacks. It was the most satisfying conflict I ever had in a Civ game because my decisions about where I placed my units made a huge difference to the war, which isn't something that I felt was true of Civ IV.