delegation of meetings between nato and russia on wednesday. cnn s nic robertson is in geneva with a look at what led to these talks. russia s troop buildup on ukraine s border triggered t tensions. by mid november, close to 100,000 troops, u.s. nato fearing an invasion of ukraine, and russia claimed they were doing exercises and training on their own soil and wanted to have talks. president vladimir putin got joe biden s attention and a video call. biden warned putin an invasion would prove sanctions. the uk backed him up.