dakar long-awaited multi-national military force africa sahel region begin operations counter escalate islamist insurgencies participants joint effort say thursday g5 sahel force back france unite state launch campaign oct. 28 amid grow unrest desert reach sahel jihadists al qaeda islamic state-affiliated group roam undetected often across long porous border last month islamist militants kill four u.s. soldier least four nigeriens ambush highlight risk operate remote region g5 sahel make troop mali niger chad burkina faso mauritania police region collaboration 4,000 french troop deploy since intervene 2013 beat back insurgency northern mali first mission call haw bi comprise several hundred soldier mali niger burkina faso whose share borderlands epicenter surge militant attack g5 sahel say statement operation ... aim achieve area control region three border fight arm group traffic order allow return level security favorable tranquility populations statement say force eventually swell 5,000 men battalions also engage humanitarian development work say g5 sahel whose command base sevare central mali also coordinate minusma mali u.n. peacekeeping mission minusma face frequent attack north islamists regain grind since 2013. new force face number challenge least fund unite state week promise 60 million support fell short hop france others washington would back direct fund unite nations g5 sahel launch military operation african scrublands