Zeljava Air Base, Bihac, Thursday, 15 April 1948
Major-General Rupnik had arranged the test of the Italian air defences with meticulous care. The normal radar chain that guarded the Italian frontier had been reinforced by several mobile units brought up from the vicinity of the capital to extend the over watch capacity of the network. Agents operating on the Italian side of the border would give warning – as best they could – of any special preparations, and would report afterward their observations. Fighter patrols operating over Yugoslavia were on alert to react as necessary to respond to any Italian ‘hot pursuit’ of the Yugoslav Arado chosen for the mission.
Despite the preparations, despite the apparent laxness of the Italian defenders, Rupnik knew that there were too many things that could go wrong. He had come to the war room of the Zeljava air base to monitor the operation personally. The Arado reconnaissance aircraft, equipped with cameras, would cross the Italian frontier in the vicinity of Karlovac, flying westward towards the Italian-occupied port of Rijeka, where, if all went well, it would photograph the activity of the Italian fleet there. While some of his staff had suggested that the aircraft’s flight be extended to the look into the port of Pola, Rupnik had vetoed such a move as too risky. What they were doing was sufficiently dangerous.
The ground controllers were monitoring all activity along the frontier, and when the Arado was plotted as departing Yugoslav airspace the tension in the room was palpable. Flying high and fast the Arado should complete its mission before any Italian aircraft could rise from their airfields to interfere; any standing patrols of fighter aircraft would be a different issue – they might have sufficient time and altitude to intercept. Thus far however, the data from the Yugoslav radar network did not identify any such preparations.
The clock clicked onward; in his mind Rupnik reviewed the course the aircraft was to follow – skirting Vrbovsko, Ravna Gora, and Delnice before crossing the final range of mountains and starting its approach run to Rijeka. His eyes were riveted on the plotting board, where the markers that would have indicated the position of Italian aircraft lay unused. The reports coming in from all quarters suggested no response – a circumstance Rupnik took no solace in – it could merely mask a trap set by the Italians.
By now the Arado would have reached the vicinity of Rijeka; Rupnik hoped that whatever its cameras recorded would be worth the risk taken. After accomplishing its mission, the Arado would held south and then southeast along the coast, turning inland in the vicinity of Selce and again climbing over the mountains that framed the limits of Italian-occupied Dalmatia.
One of the monitoring controllers spoke, “Our radar station at Plaski reports our aircraft approaching, nothing else on their screens”. Rupnik watched the markers moved – at least the Arado was now back in Yugoslav airspace – without any reaction on the part of the Italians it would seem. The tension in the war room evaporated.
The signals network monitoring Italian communications though was quite busy. Intercepted messages – some in code, and some in the clear, indicated that the Arado had been spotted and perhaps tracked, though the first Italian aircraft detected on the Yugoslav radar did not appear until the Arado had reached Yugoslav territory – which suggested a very poor state of readiness on the part of the Italians. No attempts were made to follow the Arado. Rupnik hoped that the intercepted transmissions might be prised open to yield more intelligence upon further analysis, but for the moment, he had gambled and won. No doubt Rome would protest, and might even attempt something of its own. But that would be another day.