What dispute did Stalin and Churchill have at the Tehran Conference?

Most of the Tehran meeting was spent discussing military issues. After the Big Three introduced the situation on their respective battlefields, they focused on the issue of quickly opening a second battlefield requested by Stalin. Although Churchill did not verbally oppose Operation Overlord, he used various reasons as an excuse to avoid direct combat with the main force of the German army. He was to conduct a Mediterranean campaign and advance into the Balkans while Italy was rapidly advancing north. Churchill called his proposal a "strategy of encirclement." Stalin asked American and British troops to land in northern France in May 1944 to open a second battlefield. Churchill said he could not guarantee that. The dispute between the two sides was so fierce that Stalin stood up angrily and said to Molotov and Voroshilov: "Let's go! We have nothing to do here, and we still have a lot to do on the front line!" Later, with Roosevelt's mediation and participation, the meeting was able to proceed.