Re Murray, the briefest of summations; LGen Murray was the commander of Anglo-Italian-Spanish forces on the east coast of Spain. He missed an opportunity of isolating one of Suchet's divisions during the second Battle of Castalla in 1813. His caution here can be forgiven as a missed opportunity.
However, the same cannot be said of Tarragona. At Tarragona he landed a large army from the sea to lay siege on a small French garrison, which was expected to be quick an easy with his overwhelming force and naval support. In fact the garrison commander was prepared to surrender after a token resistance to maintain his honour.
The plan, after quickly subduing the fortress, was to unite with a Spanish army moving along the coast and engage Suchet's army and drive it north to the Pyrenees. His main operational objective was to keep Suchet's army from interfering with Wellington's inland advance.
After beginning the siege he received false intelligence that Suchet's army was near Tarragona. Murray's forces were making good progress when he ordered the lifting of the siege and immediate embarkation of his army despite the protests of his commanders and the Royal navy. Many tons of guns, ammunition and supplies were abandoned.
The Spanish commander was abandoned without discussion and left to his devices. He retreated further south to the start point. The naval commander viewed Murray's actions as a precipitous and unnecessary retreat and tantamount to cowardice. He reported the debacle to the Admiralty, which generated a court martial.
For a good account of this situation and the eastern campaign see "Wellington's Eastern Front", by Nick Lipscombe.