al udeid air base qatar even tensions unite state russia fester one surprise place military-to-military contact quietly weather storm syria four months since u.s. president donald trump order cruise missile strike syrian airfield allege chemical weapons attack june u.s. military shoot syrian fighter aircraft first u.s. down man jet since 1999 also shoot two iranian-made drone threaten u.s.-led coalition force u.s. russian military officials regularly communicate u.s. officials tell reuters contact help draw line map separate u.s.- russian-backed force wag parallel campaign syria shrink battlefields also telephone hotline link former cold war foes air operations center u.s. officials tell reuters 10 12 call day hotline help keep u.s. russian warplanes apart support different fighters grind small task give complexities syria civil war moscow back syrian government also aid iran lebanon hezbollah claw back territory syrian rebel islamic state fighters u.s. military back collection kurdish arab force focus firepower islamic state part strategy collapse group self-declared caliphate syria iraq reuters give rare access u.s. air force hotline station inside qatar-based combine air operations area last week include meet two russian linguists native speakers serve u.s. interface conversations russian commanders conversations easy contact two side remain resilient senior u.s. commanders say reality work hard problems general find way maintain deconfliction line separate u.s. russian areas operation find way continue mission lieutenant general jeffrey harrigian top u.s. air force commander middle east say interview side scramble capture leave islamic state caliphate risk accidental contact grow negotiate sometimes phone call tense us protect coalition partner destroy enemy harrigian say without comment volume call risk miscalculation come full view june unite state shoot syrian su-22 jet prepare fire u.s.-backed force grind u.s. officials speak condition anonymity say aircraft area incident unfold two russian fighter jet look american f-22 stealth aircraft keep watch even high altitude tell reuters incident moscow publicly warn would consider plan fly west euphrates river target u.s. military keep fly area keep talk russia russians nothing professional cordial discipline army lieutenant general stephen townsend iraq-based commander u.s.-led coalition tell reuters syria u.s.-backed force consume battle capture islamic state former capital raqqa half city retake islamic state officials say talk underway extend demarcation line separate u.s.- russian-backed fighters grind fight push toward islamic state last major syrian stronghold deir al-zor region line run irregular arc point southwest tabqa east point euphrates river along euphrates river direction deir al-zor say u.s. defense secretary jim mattis visit jordan week say line important u.s.- russian-backed force come close proximity communication syrian regime russians deal mattis say continue procedures right euphrates river valley bisect euphrates river deir al-zor oil resources critical syrian state province largely hand islamic state become priority pro-syrian force also crosshairs u.s.-backed syrian democratic force sdf sdf spokesman talal silo tell reuters last week would sdf campaign toward deir al-zor near future though sdf still decide whether would delay raqqa fully take islamic state syria war tighten u.s. russia military hotlines hum