NATO commanders have made no secret of their frustration at the limits imposed on their bombing tactics in the war.
Gen. Wesley Clark, the top commander of Operation Allied Force, ordered his staff to draw up a campaign plan that would avoid any allied casualties, according to officials here. That unusual requirement has meant NATO pilots generally fly no lower than 16,000 feet, staying out of range of most Serbian antiaircraft fire.
At the same time, NATO diplomats say their pilots are trying unusually hard to avoid civilian casualties - a criterion that sometimes obliges them to abandon a mission if their target is too close to civilians.
These twin limitations are born of political fears that public support for the war in the United States and Europe - already showing signs of fraying - could drop fast if too many people get killed.
"That does put constraints on NATO doing as much as we want as quickly as we want," says one NATO diplomat. Without those constraints, "we could use a much more robust bombing campaign."
As it is, pilots are obliged to fly high, which makes it harder to spot targets, and ordered to attack them only if they are far from civilian settlements.
"It is very difficult to pick out targets ... individual tanks and APCs [armored personnel carriers] from high altitudes," the diplomat adds.
Destroying the sorts of target present in Kosovo, such as dispersed and isolated tanks, APCs, and units of men, is also a slow business.
It takes one smart bomb to destroy one artillery piece; it often takes several bombs to destroy a building, and an airfield could have as many as 30 or 40 buildings on it.
Unless NATO puts its pilots at more risk by flying lower, or puts civilians at more risk by bombing less selectively, the Yugoslav Army will still have the means to defend itself even after several more weeks of intensive bombardment.
"In the end," says a senior diplomat, "you can never win the war, you can never occupy territory, from the air."