What events in last 12 hours hint at a widening Middle East war?

Houthis attacked Saudi Arabia's capital on Saturday amid ongoing conflict. Following this, US State Department warned all American embassies in the Middle East to exercise caution. US' heavily-loaded B-1B bomber took off for an undisclosed location from UK. Iran has reportedly issued 'Code 100', the highest military alert. US President Donald Trump cut short his trip and returned to Washington.