Russia has amassed an estimated 9-10K troops in the region of Kursk near Ukraine's border, Ukrainian officials and military observers said on Tuesday — signaling that Russia may be preparing to launch an assault on the Sumy region of Ukraine.
On May 10, following similar warnings of troop build-ups, Russia opened up a new front in the war by launching a cross-border offensive into Ukraine's northeastern Kharkiv region. It has since captured a number of villages and settlements there.
These Russian groupings of troops are limited, understaffed, and disjointed therefore it's unlikely they will make serious advances. However, their presence extends the frontline further so Ukraine needs to be prepared to handle this development.
With Ukraine's Western partners providing it with long-range weapons that have an increased range, it was necessary for Russia to create this buffer zone inside Ukrainian territory so that it could keep Russian citizens safe.