Both the Anglo-French and the Soviets desired a concrete assurance on the others willingness to fight. With this in mind, a guarantee was made by both sides that within six months of war with Germany, each would have launched a major offensive if the other had been attacked, or both would launch an offensive if neither had been attacked. If this deal wasn't honoured there was an acceptance that the Alliance would be abandoned and peace would be made with the Germans. The deal seemed to please both sides, each being given something of an insurance policy should the other choose to play the alliance for their own gain with the fear of a stronger Germany. Then Stalin began to squeeze.
To further the aim of making any war two-front as soon as possible, the Soviets proposed that they station a quarter of a million troops in Poland and the Baltic States to be able to stick to this commitment as well as being able to more effectively help Poland defend itself if it were attacked. The Poles refused this out of hand, they were unhappy enough about any alliance with the Soviet Union. Soviet troops on Polish soil, even during a war, was a nightmare. The Soviets ensured the Poles of their peaceful intentions, arguing that this was the only way they could keep their commitment of an offensive within six months. The British and French were divided over the issue. The French, a continental power, were much more eager to have an alliance with the Soviets secured and suggested that the Polish be told to accept the Soviet offer or lose any guarantee of security whatsoever. The British, who still believed that war could be avoided even without an alliance with the Soviets, were less eager to put the Soviets in a position where they could take over Poland in the blink of an eye. The French valued the British an ally more than the Soviets however and went along with the British line of politely telling the Soviets that they could not dictate to the Polish what their foreign policy would be. The Soviet response of 'You didn't mind telling the Czechs' did not end the talks but it ended any hopes of a once strong alliance.
The Soviets explained that, eager as they were for an anti-fascist alliance, they could not enter into one were promises would be disregarded. If they could not keep their commitments then what obligation had the British and French to avoid watching the Germans and Soviets bleeding each other white. Dealing came down to more basic requirements, could the Soviets be persuaded not to make a deal with the Germans? The final deal remained controversial, and largely secret. Officially talks broke down, but a deal had been made. The Soviets would not become bedfellows with the Germans, and in exchange the British and French would turn a blind eye to Soviet encroachment on the Baltic states.
Neither side was happy, but the Germans were unhappier still.