Fortified: A Sign of Weakness?
When Moses sent the spies to scout the Promised Land, he gave them specific instructions on what they should look for. The purpose of sending these spies was to prepare the children of Israel for the conquest of Canaan. Since conquest involves combat, they had to be apprised of the military and strategic strength of the Canaanites.
Moses instructs them to see what kind of cities there were in the Land of Canaan:
“And what of the cities they live in: are they open cities or in fortresses?”
Taken at face value, it would seem that if the cities were fortified, they must prepare themselves for a formidable struggle to penetrate Canaanite defenses. That level of effort would not be as necessary if the cities were open.
However, Rashi makes the very opposite case.  He states that Moses implied that if the Canaanites live in open cities, they must feel so secure because of their strength that they don’t need to fortify their cities with impregnable walls.  On the other hand, if the cities are well fortified it is a sign that they are insecure and do not believe they can rely on their own strength, depending instead on the fortifications around their cities.
The spies returned with a negative report, intended to frighten the people and dissuade them from entering the land.  They seem to reject Moses’ assessment and embrace the opposite narrative, that fortified cities would make the conquest that much more difficult.
“However, the people who inhabit the land are mighty, the cities are fortified, extremely huge, and we even saw there the sons of giants.”
Commentators (See Mizrachi and Gur Aryeh) ask how it is that their report of fortified cities contradicted Moses’ assessment? The spies reported, on the one hand, that the people were mighty, yet they also reported that the cities were fortified.  Didn’t that contradict Moses’ assessment that fortified cities are actually a sign of weakness?
Compounded Strength
One possible way of explaining the discrepancy is that Moses was telling the spies how they could tell if the Canaanites were weak or strong without actually meeting the people. Moses did not intend them to make close contact with the people to determine their strength. He was coaching the spies to determine their strength without coming too close by observing whether the cities were fortified or open.
However, when the spies scouted the land they actually came into contact with the people and observed ferocious giants in whose presence the spies appeared no bigger than grasshoppers or (as Rashi states) ants. Once the spies were convinced of the strength of the Canaanites, they concluded that the fortifications were not signs of weakness but a sign of additional strength that would make the conquest impossible.
Mivtzarim or Bitzuros: A Distinction Without a Difference
Another way of answering the question is to cite the commentary of Rashi on the words the spies used in their description of the cities. The word used in the Torah is bitzuros-fortified, which seems to be related to the word Moses used, bmivtzarim.
Rashi, however, comments: “Bitzuros: This denotes strength. Targum translates it kricihin which means circular fortified structures. In the Aramaic language the word crich means round.”
Why did Rashi explore the meaning of the word bitzuros when it is so similar to the word b’mivtzarim on which Rashi did not comment?
Perhaps Rashi was troubled by the question raised above: why were the cities fortified if the Canaanites were so strong, contrary to Moses’ “theory?”
To respond to that question, Rashi says that in fact the spies did not just report that the cities were fortified, but that the walls surrounded the cities. They were fortified on all sides, which meant that the enemy would fight ferociously because there would be no route of escape. There is a law that when the Jewish people fight their wars, they must allow the enemy a route of escape because the resistance would be much stronger if there were no escape, resulting in a much higher casualty figure.
Therefore, the spies were saying that the cities are completely surrounded and would fight much more fiercely. 
Different Perspectives
On a deeper level one could explain the discrepancy between Moses’ assessment of fortified cities and that of the spies.
Moses’ perspective was that the conquest of Canaan was a fait accompli. G‑d would certainly make good on His promise and they would successfully conquer the land. So, when Moses gave the spies instructions, he did not question the inevitability of the Israelites conquest of the Land of Canaan. The only reason to send the spies was to allay the Peoples’ fears and embolden them to undertake the conquest. Moses wanted them to see for themselves how the conquest was eminently possible.
Moses was certain that whatever they observed would enhance their trust in their ability to conquer the land.
So, when Moses instructed them about the cities, whether they were open or fortified, he meant to impress upon them that either way it was a positive sign. Obviously, if the cities were unfortified it would be easier to conquer them. But even if it turned out that the cities were fortified, Moses wanted to impress upon the spies that that, too, was a positive sign. It was a sign that the Canaanites were weak and did not rely on their own strength. Moses saw blessing and opportunity in whichever scenario was true.
However, the spies set out with a different attitude. Their perspective was negative, which led them to see everything in negative terms. Thus, when they saw fortified cities, they took it as a negative; as a sign that it would be very difficult to penetrate those cities and defeat the enemy.
Two people can look at the same event and see different possibilities. The positive person, who is imbued with faith, will see the positive even where it appears to be negative. The negative person will see things as bleak even when they appear bright.
All Signs Point to Redemption
The lesson for our own time is clear.
We’ve been told numerous times by the Rebbe that we are living on the very cusp of the Final Redemption through Moshiach. The Rebbe quoted the words of the Midrash that predict conflict in the Middle East and that G‑d says to the Jewish people: “All that is happening should not frighten you because it is all happening for your sake.” Moreover, the Midrash declares that Moshiach stands on the [metaphoric] roof of the Bais Hamikdash and declares “Humble ones, the time for your redemption has arrived.”
This Midrash echoes what we see from Torah. Everything that happened on the cusp of the conquest of the Canaanites was a positive sign despite appearances to the contrary.
Similarly, everything that is happening today is a sign that we are entering into the Messianic Age. Even those negative things, which we pray should be averted and cease, are signs of the imminent Redemption.
It’s up to us to decide whether we see things through the eyes of the Spies or through the eyes of Moses and Moshiach!