BAGHDAD – The United States has been fighting what officials term a silent war with Syria which killed at least five soldiers over the weekend. U.S. officials said U.S. Marines have deployed along the Syrian border to stop the flow of insurgents and equipment to Iraq. They said marines have engaged with both Sunni insurgents as well as some Syrian security personnel along the border in clashes that have intensified over the last few weeks. The U.S. military presence – increased by more than a third over the last two months – was said to be focused on the western Iraqi towns of Al Qaim and Qusaybah, regarded as key points in the smuggling of insurgents and weapons from Syria to Iraq.