Russia landed attack helicopters and troops at a sprawling air base in northern Syria vacated by U.S. forces, the Russian Defence Ministry’s Zvezda TV channel said on Friday. Armed Russian military police were shown in footage aired on Zvezda flying into the Syrian air base in northern Aleppo province near the border with Turkey and fanning out to secure the area. The move comes after U.S. President Donald Trump abruptly ordered the withdrawal of U.S. troops from parts of Syria last month.