It's been explained & now the proof is in the pudding (that is a really stupid expression)
Washington Times said:Iran massing troops on Iraq border
Beirut, Lebanon, Jun. 15 (UPI) -- Iran reportedly is readying troops to move into Iraq if U.S. troops pull out, leaving a security vacuum.
The Saudi daily Al-Sharq al-Awsat, monitored in Beirut, reports Iran has massed four battalions at the border.
Al-Sharq al-Awsat quoted "reliable Iraqi sources" as saying, "Iran moved part of its regular military forces towards the Iraqi border in the southern sector at a time its military intelligence agents were operating inside Iraqi territory."