Armies may very well march on their stomachs, but when enough stomachs get together, when 2,600 (count-em, 2,600) hoohas and nabobs of the Democratic Party meet to eat, an army is what is needed to see that they all get fed at the very same time.

And on Tuesday afternoon, the five-star general of this operation, Peter Schall, director of catering for the Washington Hilton, site of last night's Democratic Congressional Dinner, could be found in his office re-enacting a scene out of any number of Hollywoodwar movies - leaning forward at his desk, he was pointing to a large chart unrolled in front of him, moving men and materiel as a trusted aide leaned attentively over his shoulder.

Yet instead of troops to the front Schall was moving tables to the Hilton's enormous football-shaped ball-room, trying to find room for all those hoohas and nabobs, trying to make sure there would be enough aisle space for the 180 waiters and 12 captains to serve them the food that had been purchased in mind-stirring quantities.

Consider for instance a fruit salad that needed 470 pounds of fruit, including an even 100 of honeydew and of the cantaloupe. Or a spinach and Boston lettuce salad that used up 20 cases of Boston lettuce, 22 cases of spinach and 8 flats of mushrooms (a total of 496 pounds), not to mention 30 dozen eggs. Or 740 pounds of broccoli, 720 pounds of potatoes, 230 gallons of ice cream, and lots and lots and lots of filet mignons.

"We like to have numbers like that," Schall said, smiling and looking genuinely pleased while noting that the Hilton has had bigger single functions - the Congressional Black Caucus dinner at over 3,000 people was one - and is in fact capable of serving 8,000 at once should they want to squeeze themselves into all its various nooks and crannies.

Born in Germany and a graduate of its hotel schools, the 35-year-old Schall started at the Hilton as a waiter in 1965. An efficient-looking man who seems to delight in the circus-ringmaster aspects of his job, he says it couldn't be done - you couldn't even feed one Democrat, let alone 2,600 - if it weren't for fierce advance planning

"You have to have absolutely everything completely covered, that's one of the key things," he says as he hurries between his office and the ball-room and the kitchen and the florist. "If you don't have it down pat before-hand, you can't function. If I had to worry if the food was here, I couldn't take care of last-minute details when things start to get hectic." When asked to describe what his job is like on banquet nights, "hectic" is the word Peter Schall turns to most.

Planning for last night started back in July, when Schall and the Democrats blocked out preliminary dates. The Dems had used the Hilton in years past and liked it because all seats in the ballroom were unobstructed and because some canny person had thought to consult the Secret Service while it was being built.

The result was a series of elevators and passageways which enabled the President to whisk from his limo into his own little holding room - complete with a direct line to the White House and pale-green "J.C." embossed towels - and from the holding room onto the stage without being exposed to so much as a scintilla of danger.

In the beginning of January Schall met with Janet Howard, director of the House and Senate Democratic Council and specific decisions started being made.The tablecloths would be white, for instance - an elegant color. And the main course would be filet mignon because it was felt that that's what people who paid $500 per plate expected.

Deciding on appetizers, vegetables and desserts proved more troublesome, so a test dinner where all the possibilities were cooked and served was held in February. Out of this came the decision to have fruit, not soup, for a first course because soup took longer and could get, well, messy, and to have the wonderful sounding gateau glace maison with strawberry sauce as finale, presumably because it tasted just yummy.

As soon as the menu was formalized, Schall sent out 38 copies of a ditto sheet to l2 different hotel departments. The chief of security, for instance, needed to know that the volume of traffic would mean that T Street would have to be made one-way. Even the garage was contacted so that guests could pay for parking on the way in and, in Schall's words, "not have to sit a long time in fumes" on the way out.

The most important person contacted was executive chef Barry Thompson, a cheery 36-year-old native of England who says that "knocking out 2,500 filets" gives him as much satisfaction as cooking an in-time little French dinner. And vice versa.

About 10 days before the banquet, Thompson sat down with the hotel's purchasing agent to work out how much of what need be bought, while taking into account things like "what is the availability of fresh strawberries given all the rain in California."

Thompson prefers to use fresh vegetables, and in fact the 200 pounds of zucchini and the 180 pounds of eggplant used to make enough ratatoville to stuff 700 pounds of tomatoes would be fresh. But, sadly, the 740 pounds of broccoli would be frozen simply because the cost of cutting up and preparing the fresh kind would be prohibitive.

On Tuesday, the day before the banquet, the kitchen slowly moves into gear. The 22 cases of tomatoes all get their insides scooped out and are put into the icebox uncooked. The filets are trimmed and put into another icebox on large pans. The spinach, all 22 cases, is taken out of its little plastic sacks, just like you see in the grocery, washed and cleaned. The broccoli is blanched (heartlessly plunged into boiling water) so that it can be quickly cooked on Wednesday. The fruit is cut up so it can be marinated in kirsh overnight. And that wonderful dessert is hidden away in a far icebox, away from illicit hands.

Yesterday, banquet day, Peter Schall arrived at the hotel at 7:30 a.m. and planned to stay at least till 1 a.m. His desk calendar has a big "X" on it, which means he has no appointments, but will spend all that time on his feet checking everything out while staying in constant touch with his office via a beeper system. He calls days like this "being on the bicyle."

Early in the morning the Democrats call to up the head count (which had stood at 2,300 on Tuesday) to 2,510. So Schall had to put in more tables and call his local purveyors for more meat, a process he would have to repeat when the Democrats again up the tally - to 2,600 - in the early afternoon.

Schall's major problem for the day was that the center of the ballroom would be occupied until 4:30 by a meeting of the American Association of Dental Schools. So while the 100 or so tables in the two wings could be set up, everything had to be in readiness to move into the center as soon as the meeting broke up.

Also on Schall's mind was the time that would have to be taken to brief the waiters about things like not clearing away dishes during the national anthem, as well as the time when everyone would have to leave the room so the Secret Service and its dogs could check it out for possible menace.

Yet all these challenges seemed, if anything, to galvanize rather than dismay him. "This," he said in reference to it all, "is the exciting thing in our business."

In the kitchen Barry Thompson was feeling pretty much the same way. At around 8 a.m. the fresh fruit was put in little cups and the salads were dished out. "They can sit very happily in the icebox for six hours." he said, "but you can't put the dressing on until the very last minute or it'll get mushy."

Just the opposite are the steaks, the last thing cooked. Prepared basically by two people who work in front of a bank of five 600-degree broilers, each with three tiers, they are put in at the ultimate moment - "It takes really good teamwork between myself and the banquet headwaiter, telling me when people are filing in" - because the intense heat ("instant sunburn") means that only a minute or two too long and "you've got pot roast and a lot of unhappy people."

Though the whole operation has the feeling of the beach at Normandy, the truly amazing part, says Thompson, is that the hotel does this kind of thing all the time.

"The revenue coming in and all, God bless it, it's wonderful, but really it's nothing special, this hotel is geared for it," he says with the off-handed pride of a driver whose car has just broken the world land speed record. "It's a meat and potatoes operation, but the timing makes it great."