RIYADH — Deputy Crown Prince Muhammad Bin Naif, Second Deputy Premier and Minister of Interior, sent out a stern warning to all those planning to destabilize the security and stability of the Kingdom that “there are men who are ready to sacrifice their lives in defense of their religion, nation, leadership and citizens.” He was speaking at the conclusion of the first joint mobilization drill for security sectors (Homeland 85). Meanwhile, Saudi security forces on Wednesday ended a weeks-long exercise on the Iraqi border where three troopers died in a January attack blamed on “terrorists.” Border Guards and other Interior Ministry units have been conducting daily training as part of the “first joint tactical” exercise north of Arar city, the Saudi Press Agency reported. The exercises began late last month. SPA said that one scenario involved repelling an attempt “to storm the border with vehicles.” That exercise included 1,500 men from the Border Guards, the high-tech command and control center, customs department and other agencies. The northern border is guarded by a double-fence system and complementary radar and camera surveillance network stretching for hundreds of kilometers. The system has become the front line in efforts to protect the Kingdom from infiltrators. That threat became painfully clear in January when three border guards, including a commander, were killed in the desert scrubland of Suwayf, north of Arar, during a battle with infiltrators who tried to enter the Kingdom from the Iraqi side despite the security measures. “To get it really watertight is almost impossible,” a Western diplomatic source said.