The Gentle Earth by Christopher Anvil, 1957

The invaders discover that humans have fission, fusion, indirect molecular and atomic reaction control, and a long reaching development of electron flow and pulsing devices. The only thing the invaders have that humans don't is keyed focusing, and that is just a matter of time. That is the one key technology holding mankind back from reaching technological parity, so they decide that the safest thing to do would be to launch a preemptive strike just in case we turned out to be hostile.

The invaders use steam trucks, which are not only unreliable in Earth's atmospheric pressure, but they lose steam out the exhaust. On their planet the aliens can just get a couple of buckets of water from a nearby stream, but they are invading a part of Earth that is undergoing a severe drought.

So they use captured Earth automobiles. Which are so fast that the invading army rapidly outruns their supply chain and makes them overextended.

The Gentle Earth by Christopher Anvil, 1957

The invaders discover that humans have fission, fusion, indirect molecular and atomic reaction control, and a long reaching development of electron flow and pulsing devices. The only thing the invaders have that humans don't is keyed focusing, and that is just a matter of time. That is the one key technology holding mankind back from reaching technological parity, so they decide that the safest thing to do would be to launch a preemptive strike just in case we turned out to be hostile.

The invaders use steam trucks, which are not only unreliable in Earth's atmospheric pressure, but they lose steam out the exhaust. On their planet the aliens can just get a couple of buckets of water from a nearby stream, but they are invading a part of Earth that is undergoing a severe drought.

So they use captured Earth automobiles. Which are so fast that the invading army rapidly outruns their supply chain and makes them overextended.

The Gentle Earth by Christopher Anvil

The invaders discover that humans have fission, fusion, indirect molecular and atomic reaction control, and a long reaching development of electron flow and pulsing devices. The only thing the invaders have that humans don't is keyed focusing, and that is just a matter of time. That is the one key technology holding mankind back from reaching technological parity, so they decide that the safest thing to do would be to launch a preemptive strike just in case we turned out to be hostile.

The invaders use steam trucks, which are not only unreliable in Earth's atmospheric pressure, but they lose steam out the exhaust. On their planet the aliens can just get a couple of buckets of water from a nearby stream, but they are invading a part of Earth that is undergoing a severe drought.

So they use captured Earth automobiles. Which are so fast that the invading army rapidly outruns their supply chain and makes them overextended.

The Gentle Earth by Christopher Anvil, 1957

The invaders discover that humans have fission, fusion, indirect molecular and atomic reaction control, and a long reaching development of electron flow and pulsing devices. The only thing the invaders have that humans don't is keyed focusing, and that is just a matter of time. That is the one key technology holding mankind back from reaching technological parity, so they decide that the safest thing to do would be to launch a preemptive strike just in case we turned out to be hostile.

The invaders use steam trucks, which are not only unreliable in Earth's atmospheric pressure, but they lose steam out the exhaust. On their planet the aliens can just get a couple of buckets of water from a nearby stream, but they are invading a part of Earth that is undergoing a severe drought.

So they use captured Earth automobiles. Which are so fast that the invading army rapidly outruns their supply chain and makes them overextended.