One military analyst expert says the Navy’s decision this week to pursue building a third Zumwalt destroyer is because of events in Georgia. Others attribute the change in direction to concerns about maintaining the country’s shipbuilding capacity.

Whatever the reason, it is not certain that a third destroyer will be funded and built. Before that happens, many questions remain about what types of ships should be built.

Last month, the Navy announced that it planned to build just two DDG-1000, or Zumwalt, destroyers. Originally, the Navy planned to build 32 of the destroyers, which were designed to avoid detection and to maneuver closer to shore than the Arleigh Burke destroyers they were meant to replace. That was later downscaled to seven and, in July, two.

This prompted concerns that Bath Iron Works, which has begun work on the first DDG-1000, would not have enough work. Similar concerns were expressed in Mississippi where Ingalls Shipbuilding was building the second.

Earlier this week, the Navy changed course and said it would pursue a third Zumwalt destroyer. The Senate has included funding for the ship in its defense budget. The House has not.

To end this deadlock, the key question to be answered is: What ships does the Navy need to fulfill its mission in coming years?

Answering that question is complicated by world affairs, says Jay Korman, a Navy-analyst for Avascent Group in Washington, D.C. The DDG-1000 was the culmination of decades of planning and design with a focus on fighting a “near peer,” like Russia or China. The stealthy ship was meant to get close to a country’s coastline before firing its weapons to clear the way for ground troops.

This mission faded in importance as the U.S. military moved toward a light and lean strategy to combat terrorists and insurgents in places such as Afghanistan and Iraq.

Then, two weeks ago, Russia attacked Georgia. Using military deterrence, in the form of more sophisticated and powerful weapons than Moscow has, was back in vogue. Mr. Korman was only partially jesting when he said the new destroyer could be called the USS Putin.

Keeping the country’s shipbuilding options flexible to meet changing demands makes sense. The challenge for lawmakers and the Navy is to determine what ships can best respond to a variety of threats and how much it will cost to build them.

Rep. Tom Allen had it almost right when he said, “We ought to be building the ships the Navy wants.” The ships the Navy needs are the ones that should be built.