In Command
Spock is so often called "the perfect first officer" that it can be easy to overlook his considerable abilities in the command chair. His style is quite different than Kirk's - but equally effective. It's unfair for both his shipmates and viewers write Spock's missions off as failures. They are often quite successful, and carried out against impossible odds.
Kirk is similarly saddled with an unfair reputation: he is not a loose cannon but works according to expectations. His superiors expect him to carry out his missions no matter what it takes, and he certainly does this. His officers expect him to listen to their advice and concerns, to reassure them in crises, to reason, to bluff, to fight, to take risks at the crucial moment. He keeps a steady rein - "I'll keep that in mind . . . when this becomes a democracy," he says in The Corbomite Maneuver - but not too steady. Though occasionally overbearing, Kirk is the paradigm of a starship commander.
When Spock takes the conn, he's apt to defy expectations the commander's role. His officers must to perform their assigned tasks: no more, and certainly no less. The Vulcan provides no inspiring speeches, and refuses to mask less-than-pleasant truths. He'll listen to others' ideas, but judges the ideas as sound or not, and will not carry them out as a favor. Despite his Vulcan devotion to peaceful solutions, Spock prefers confrontation to fruitless negotiations, and does not bluff. When in command, he's in control, and puts his principles of decision-making based on logic into practice.
The Enterprise crew is content with Kirk, but resents Spock's relentless rationalization. The Vulcan does not act on intuition or "common sense," which often prevents him from taking the most straightforward course. The officers often don't understand why they're given certain orders, and take them as madness rather than logic. Spock sees no need to explanations his choices, but hopes the mission is finished as quickly and efficiently as possible.
"Rush jobs" do get Spock into difficult situations, as does his disregard for crew morale. His judgment calls are not always fully sound, his "calculated" risks extreme. But these traits must be weighed against his insight, innovative strategies, and perseverance. With Spock in charge, it's sure to be a wild ride, but one that reaches its destination.
The crew of the shuttlecraft Galileo certainly experience this in The Galileo Seven. Stranded on a barren alien world, Spock finds himself heading up "his first command", as McCoy glibly points out. Previously he had only minded the ship, with Kirk in reach on a deck or planet below. Spock tells the doctor that yes, he'll be doing things logically.
Despite the Vulcan's best efforts, two men are killed under his watch by planet's tribal inhabitants. It doesn't so much bother those remaining that the officers are dead - after all, many ensigns die in the line of duty under Kirk - but that Spock shows no signs of grief or regret. Later the crew begs for inspiring words as the shuttle is attacked, but their commander only sorts through facts. Spock hears several times the phrase "sick and tired of your logic." Yet his final act as the shuttle's orbit decays is taken on impulse: jettisoning the fuel and creating a flare. The Enterprise comes to the rescue and Spock is teased for his "emotional" decision. Yet this choice saved five lives and was correct by Spock's reasoning.
Spock's turn to command the Enterprise itself arrives in The Tholian Web, in which Kirk is caught in another dimension as space overlaps. His efforts to recover the captain are thwarted by the Tholians, who construct a energy field in which to trap the ship. Their use of power interrupts the "interphasing" of the two dimensions. Spock makes a decision to fight the enemy ships, and the traded blows cripple the Enterprise.
McCoy sees his opportunity to strike. He accuses the Vulcan of risking Kirk's recovery for a fight, perhaps true. Spock orders McCoy back to his laboratory. Only Kirk's last taped orders ease the tension, since he tells his friends to work together. The implication is that it takes both a Spock and a McCoy to equal a Kirk. Indeed, whenever Spock is in command in TOS, McCoy is present and more than willing to give advice. Into the third season Spock probably considers the doctor's presence on the bridge an inevitable nuisance but necessary and occasionally helpful. They do rescue Kirk from interspace.
By The Wrath of Khan, Spock is captain of the Enterprise, which has become a cadet training ship. Starfleet might consider him to dangerous in the field, deciding his wisdom and experience would be best applied to a controlled environment. But this position is not something Spock resents, as he enjoys his teaching duties. He also has no qualms about handing the ship back to Kirk once real danger strikes. In The Undiscovered Country, he's able to take charge in every way after Kirk is kidnapped, receiving not one complaint and solving several mysteries surrounding the Klingon/ Federation peace conference.
Spock lacks the will to command, but not the skill. He's rescued Kirk when the captain had been ferried off to numerous planets, and - as discussed above - pulled through in difficult situations. His unique approach to the challenges of command holds viewers' attention and allows for contrasts with Kirk. Spock himself accurately sums up his attitude in The Galileo Seven: "I realize that command does have its fascination, even under circumstances such as these, but I neither enjoy the idea of command nor am I frightened of it. It simply exists, and I will do whatever logically needs to be done."