Kossuth could dispatch people to block the official representatives of Austria, but they were powerless against those secretly siding with Austria.
The Hungarian Revolution was not achieved through bloodshed, meaning a large number of people inclined towards the Vienna Government remained within the country. Kossuth had thought of purging these elements, but it was simply not feasible. (The losses of a few individuals were negligible)
The internal relations within the Kingdom of Hungary were intricate and interconnected; the nascent Hungarian authority was fragile and could not withstand turmoil.
Vienna
Upon receiving the news that Hungary had expelled the Austrian representatives, everyone knew that war was on the countdown. The Austrian Government could not possibly let Hungary become independent.
"Prime Minister, how is the preparation of materials going?"
