Sam joined the Royal Marines in 2006 and served in Afghanistan in 2008-9. Towards the end of their tour, Sam was concussed by a bullet, but insisted on taking part on that day's patrol. His company became divided and his group soon found themselves under heavy enemy fire. Sam's corporal was badly wounded. Sam stepped out in front of the unit and used his heavy machine gun to fire at the insurgents who were just 15 metres away. Another man was hit. As his friends were dealing with the wounded and radioing for assistance, Sam was running out of ammunition. Whilst the unit retreated, Sam put down his gun and reached for his 9 mm pistol, keeping the enemy at bay despite being completely exposed to heavy and accurate enemy fire. The whole unit survived.
Later in 2009, Sam was doing some 'adventure training' (surfing in Newquay) when he received an urgent summons back to base. Sitting in the jeep, he wandered what he might be in trouble for. When he walked into the mess, he was handed a telegram and a glass of champagne. He was to be decorated.
Sam was awarded the Military Cross for gallantry by the Queen at a ceremony at Windsor Castle in November 2009.
On 27th May, 2011, Mne Sam Alexander was killed by an IED in Helmand province alongside his patrol leader.