Who would act as President Bush's defense secretary if Pentagon chief Donald H. Rumsfeld (search) were to resign, become disabled, die or be temporarily absent due to an overseas trip, such as on the one he began Thursday? For years the answer was, quite naturally, the deputy defense secretary.

But the answer had to change Thursday because of a simple, inconvenient fact: There is no deputy defense secretary.

There is, however, a Navy secretary.

That post is held by Gordon England (search), who also happens to be Bush's nominee to replace Paul Wolfowitz (search) as deputy defense secretary. But England's nomination has been stalled for weeks due to a dispute over whether England must buy insurance on the pension he earned before joining the government.

On May 13, the day Wolfowitz left his defense job, Bush designated England to be the acting deputy secretary. England also retained his Navy job.

The presidential executive order spelling out the line of succession to act as defense secretary says no one in that line can become the acting secretary if he holds his own position in an "acting" capacity.

So, with Rumsfeld having left Thursday on an extended trip to Asia and Europe, the only way he could have England fill in for him legally was to have Bush issue a directive that altered the line of succession.

That is just what the president did.

He directed that Navy secretary would "act for and perform the duties of" the secretary of defense in the event of the secretary's death, disability, resignation or temporary absence.

In practice, Rumsfeld retains the authority to perform his duties as secretary while he is traveling abroad. But if he cannot for some reason, England would be in line to fill in.