The surveillance scheme was working perfectly: German intelligence operatives were watching and listening to two terror suspects living in their country for more than two years. The eavesdropping was yielding a plethora of detail on the cells' desires, plans, and unusual source of funding. The hope was the spying would go on for a long time - long enough to grab others involved in the network. Instead, according to a European official knowledgeable about the operation, the two terror suspects suddenly made plans to move to the Netherlands. The German agents - unsure if they would lose contact - moved in and had them arrested this past weekend. "The arrests weren't planned," says the European source. "This story from the intelligence and law-enforcement sides now, sadly, is over."In the end, the surveillance operation offers an inside look at some of the problems and progress of those on the frontlines of the war on terror. For one thing, it shows that successes are occurring: In addition to the two suspects arrested in Germany - and the information gleaned during the surveillance operation - two other high-level terrorists were apprehended this week in Iraq. Second, it illustrates how difficult it is to tap into terrorist cells and gather enough information to stop a specific attack or round up all those involved. Third, it highlights how contentious the relationship can be between intelligence agencies and local police, which often have different mandates and goals. "My former service was in the business of letting people run in order to scoop in as many as possible," says Stella Rimington, the former head of MI5, Britain's domestic intelligence service. "But we have to work with the police, and they are of course anxious to bring things to a conclusion without taking too many risks."