Market players in Japan took the start of the U.S. assault in Afghanistan in stride Monday, wondering instead whether a drawn-out war will deal a critical blow to an already fragile global economy.

"Everybody knew it would come one day, so there is no surprise in the start of the war itself," an equities trader at a Japanese brokerage said. "The only and the most important thing we care about is how long it will last."

The United States and Britain launched military strikes in Afghanistan on Sunday night local time to begin the overt stage of an international retaliatory operation for the Sept. 11 terrorist attacks in the U.S.