ukraine as were watching whats happening to the russians now its informative for us to think about what is right from a modernization standpoint she said noting that some us tanks are very heavy and the terrain in europe is muddier not like the hardpacked sand of the desert the army she said has to determine whats the right balance between the mobility of a tank the survivability of a tank and the lethality of a tank if you want to make it more mobile you make it lighter but that makes it less survivable and so you have to decide where youre going to take risks