The US-led alliance set up what is known as the NATO Response Force in 2002, based on some 13,000 troops able to get to crisis hotspots much faster than its main forces.But the Ukraine crisis and Russian intervention in support of pro-Moscow rebels showed that the NRF might not be able to move fast enough in a vastly changed security environment, Stoltenberg said.Accordingly, in September, NATO leaders set up what is known as an NRF spearhead unit of some 5,000 troops able to deploy within days, not months.