SANAA, Sept. 21 (Xinhua) -- Six weeks after Saudi Arabia, Trkiye and Pakistan agreed in Mecca to treat an armed attack against one as an attack against all, the rapidly escalating Houthi-Saudi confrontation is putting that pledge to its first serious test. Houthi forces have advanced along Yemen's western coast toward the strategic Bab al-Mandab Strait while stepping up missile and drone attacks deep inside Saudi