What is an anvil? What dose Von Bulow Mean When he say Germany will be "a hammer or an anvil"?

Anvil is a heavy steel block that is used as a surface to hammer metal

An anvil is a heavy steel thing that black smiths use to put scolding hot fresh from the fire metal and use a hammer to shape it so they don't burn themselves. and what Von Bulow means is that germany will be the one to control or to be controlled.