Allied aircraft are being ordered to mount direct attacks on Yugoslav army and special police units committing atrocities and ethnic cleansing in Kosovo.
Serb tanks, artillery and troop concentrations in the province face low- level air attacks with laser-guided bombs, missiles and "tank-busting" 30mm cannon fire. At the same time Nato pilots will face far higher risks from anti-aircraft fire and shoulder-held missiles.
The new phase will involve an increased role for the RAF, likely with SAS and other special forces supporting their attacks.
Other aircraft would include the US A-10 Warthog armed with anti-tank missiles and armour-piercing 30mm cannon and Apache helicopter gunships used to great effect in the Gulf War.
Previous operations have been limited to high-altitude attacks with cruise missiles and precision bombing against air defence and other strategic targets. Nato commanders now feel Yugoslav air defences have been "degraded" enough to allow more aggressive action.
"This is where the gloves come off," said one military analyst yesterday. "So far we have been prancing around outside the ring doing our impression of a butterfly. Now we are going to sting like a bee."
Tony Blair agreed to increase Britain's contribution to the air armada in a conversation with President Clinton on Saturday night.
Yesterday, officials said four more RAF Harrier GR7 aircraft would be flying immediately to join the eight already operating from Gioia del Colle in southern Italy. A further RAF Tri-Star air-refuelling tanker also flew out yesterday to provide extra support, and eight Tornado GR1 bombers have been ordered to prepare for operations as soon as possible.
George Robertson, the Defence Secretary, said: "These additional aircraft, and the wider action we are now planning, will hit heavily at Milosovic's ability to pursue his murderous campaign in Kosovo. These air strikes have one purpose only: to stop the genocidal violence."
Until yesterday, due to bad weather and technical problems, the Harriers had only successfully dropped two of their Paveway II 1,000lb laser-guided bombs. Other missions were aborted, along with those of other Nato manned aircraft, to avoid dropping bombs without guidance and the risk of causing "collateral damage".
The GR7 is principally designed for a low-level ground attack role, and has infra-red technology to enable it to operate at night. It is armed with two 25mm cannon mounted underneath, and other weapons options include cluster bombs, air-to-surface missiles and twin rocket pods.
Its cold war role was close support for infantry of the British Army of the Rhine, and it works best when there are troops on the ground to direct it to targets. In Kosovo this role is likely to be performed by SAS units.
A former, highly experienced SAS soldier yesterday said this was where they come into their own - calling in air strikes using laser target designators (LTDs) against mobile, heavily defended targets.
"All they need to do is get in eye-line of the target," he said. "Then someone like me can direct them in from 50 miles away telling them what landmarks to look for.
"As we direct the aircraft in, using Tacbes - ground to air communications - we switch the LTD on for the key 30 seconds. This has a high rate of success. After the bombing we pack and discreetly leave."
There is also a method of automated LTD, used for fixed targets. "We have to get in position to place them within eye-line distance, somewhere hidden from view," said the former SAS soldier. "It might be three weeks later when the aircraft flies in to attack.
"It sends a signal which switches the LTD on and again this means that aircraft can fly fast and low, with the minimum time over target and therefore less risk of being shot down."
He was in broad agreement with the strategy so far being pursued by Nato generals.
"You can"t send in the A-10 tank-busters until the anti- aircraft is cleared," he said. "The thing pilots hate is 'time over target' - they do not like to loiter. The Serbs will have a lot of anti- aircraft equipment."
He said the School of Air Warfare accepts that a minimum of 20 per cent of attacking aircraft will not identify a target, adding to the need for accurate designation. "It is possible SAS units have been or are in parts of Yugoslavia or Kosovo to help target attacks," he said. "I do not know. There are units on the Macedonian border."
General Sir Charles Guthrie, chief of the defence staff, yesterday responded to inquiries about the use of special forces by saying: "As you well know, it is UK policy never to confirm or deny SAS or Special Force operations."
On the issue of moving to Phase II of the operation, he said: "Whilst a threat from air defences does still exist, the fact that this change of emphasis is possible results from the success of our attacks so far.
"The broadening of our attacks will now allow us to include many targets that will cause even more disruption to the Milosovic regime."
General Guthrie added: "Milosovic and his commanders should be warned that the pressure and tempo will not diminish - indeed, they will increase.
"Their unacceptable actions in Kosovo come at a high price and, for as long as they continue, that pressure will continue to rise."
Saturday 27 March
11.30am: Defence Secretary George Robertson accuses Yugoslav President Slobodan Milosevic of being "a serial ethnic cleanser" and stresses there is no weakening of Nato resolve.
4pm: US Navy launch Tomahawk missile-strike towards the outskirts of Belgrade.
5pm: Demonstrators gather in Whitehall to protest at the Nato bombing raids, and also outside the Gioia del Colle air base in Italy, where RAF Harrier pilots are stationed.
7 45pm: American Nighthawk F-117A "stealth" fighter-bomber crashes near Budjanovci, 30 miles west of Belgrade, but a rescue team is sent in to recover the pilot.
8.16pm: Phase II of Nato campaign - a search and destroy strategy against Serb security forces in Kosovo - declared by Nato Secretary General Javier Solana.
Sunday 28 March
12.05am: Serbian television shows burning wreckage of F-117A jet and says Yugoslav forces engaged in a manhunt for the pilot.
2.45am: Pentagon declares that the pilot of the stealth fighter recovered safe and well and returned to Aviano air base in Italy.
8.00am: George Robertson discloses that Arkan, a notorious Serb war criminal, is re-mobilising for Kosovo.
4.45pm: International Red Cross says it is working alongside UNHCR handing out medical supplies and food to tens of thousands of refugees pouring across border from Kosovo into Albania.
5.42pm: As Phase II continues, Paddy Ashdown goes on television to demand a protectorate be set up for Kosovo Albanians.Reuse content