The terrorists who hijacked four planes and destroyed the World Trade Center in New York killed thousands of people. But they did not kill the U.S. financial system. History suggests they won’t even come close.

The best advice for investors is to stay deliberate and rational.

When President Kennedy was assassinated in 1963, the tragedy evoked national horror and sadness. But the Dow Jones Industrial Average declined only 2.9 percent before beginning to recover. Three months later, the Dow had climbed 12 percent from the post-assassination low. (Figures are from Ned Davis Research in Nokomis, Fla.)

In the Cuban Missile Crisis of 1962, a nerve-wracking episode that posed a threat of nuclear war, stocks fell 9.4 percent over a two-month period. Three months later, they were up 21 percent from the lows.

Pearl Harbor

The Japanese attack on Pearl Harbor, which provoked a sense of national outrage and anger similar to that felt after last Tuesday’s attack, produced only a 6.5 percent decline in the Dow industrials over a one-week period. A weak recovery followed within a month. Three months after the initial decline, stocks had fallen an additional 2.9 percent but then the U.S. was in a full-fledged war.

In the days leading to the Gulf War in late 1990 and early 1991, the Dow fell 4.3 percent over about three weeks. Three months later it had risen 19.8 percent from the lows.

Regular readers of this column know that I have been partial to defense stocks for a couple of years. Unfortunately, we have just been reminded that the world is a dangerous and unpredictable place and that military force is sometimes needed.

I still like the defense stocks, but if they surge when trading resumes, there is a limit on how far I would chase them.

Northrop Grumman Corp. was trading at $81.94 when trading was halted Tuesday. I like it at prices up to $100. General Dynamics Corp. was at $75.97. I would purchase it up to $85.

Boeing Co. was trading at $43.46 before the terrorist attack. I would buy it up to $53. Raytheon Corp. was at $24.85, and I would pay up to $31 for it.

A more speculative holding is Applied Signal Technology Inc., which makes listening equipment used by U.S. spy agencies. Applied Signal has posted five straight quarterly losses and the losses have been widening. But it has no debt and sells for less than book value. The stock is at $5.19 and I would buy it up to $7, but only for clients who can tolerate a high risk.

By way of disclosure, my clients own all five of the defense stocks mentioned above.

Energy stocks

Oil prices rose in international markets following the terrorist attack, perhaps because rumors tied the attack to Palestinian liberation forces. I have been a fan of energy stocks for some time, and more so in recent months. If you don’t own them, I would buy them when trading resumes, but again I would not chase them too far.

Gold prices often rise during political crises, and gold stocks move up in tandem. Most gold stocks already sell for high multiples of earnings, though and I’m not a fan.

Telecom

It will be interesting to see what happens to the computer-related and telecommunications stocks that have been so battered this year. If they get smacked again in the next week or two, it might be wise to start buying them, rather than wait until late in the year when tax-loss selling usually abates.

Two that look especially interesting are Sybase Inc. and Black Box Corp.

Sybase Inc., based in Emeryville, Calif., makes database software and does computer consulting and technical support. It specializes in serving the financial industry and government.

Sybase lost money from 1995 through 1998. But it earned 71 cents a share in 1999 and $1.25 a share in 2000. This year, analysts expect it will earns about $1.10 a share.

In June, when the stock was near $17, Sybase announced plans to repurchase as much as 9 percent of its own stock. Today, the stock sells for only $12.20, which is less than 10 times recent earnings. The company has no debt.

Black Box Corp., based in Lawrence, Pa., installs and services computer networks and provides technical support both on site and by telephone. It specializes in serving large corporate clients. I recommended Black Box in this column last November at about $59 and it has sunk to $43.20. So that was an unsuccessful recommendation.

But I still like Black Box and more at today’s prices. It sells for only 13 times recent earnings and 11 times estimated earnings for the fiscal year in progress, which ends in March. Analysts are looking for $3.89 a share in profits, up from $3.22 last fiscal year. The company has earned a profit ten years in a row.

John Dorfman is a columnist with Bloomberg News.